CN110695533A - Method for rapid laser drilling in glass and products made therefrom - Google Patents

Abstract

The present application relates to methods of rapid laser drilling in glass and products made therefrom. Forming a hole in a material (1) comprises focusing a pulsed laser beam (2) into a laser beam focal line (2b) oriented along a beam propagation direction and directed into the material, the laser beam focal line (2b) producing an induced absorption within the material (1) that produces a defect line along the laser beam focal line (2b) within the material (1), and translating the material (1) and the laser beam (2) relative to each other, thereby forming a plurality of defect lines in the material, and etching the material in an acid solution to produce a hole having a diameter greater than 1 micron by amplifying the defect lines in the material. The glass article comprises a stack of glass substrates having pores formed extending through the stack having a diameter of 1 to 100 microns.

Description

Method for rapid laser drilling in glass and products made therefrom

The patent application of the invention is a divisional application of an invention patent application with the international application number of PCT/US2014/070459, the international application date of 16/12/2014 and the application number of 201480075631.8 entering the national stage of China, and the invention name of the invention is 'a method for carrying out rapid laser drilling in glass and a product prepared by the method'.

RELATED APPLICATIONS

This application claims priority to U.S. patent application No. 14/535800 filed 2014, 11, 07, based on 35u.s.c. § 120, which claims priority to U.S. provisional patent application No. 62/073191 filed 2014, 10, 31, which in turn claims priority to U.S. provisional patent application No. 62/023429 filed 2014, 11, 7, 11, and U.S. provisional patent application No. 61/917179 filed 2013, 12, 17, 12, 120, the entire contents of each of which are incorporated herein by reference.

Background

There is a growing interest in thin glasses with precisely formed holes for electronic applications. The holes are filled with a conductive material and are used to pass electrical signals from one part to another, which enables precise connection of a central processing unit, memory chip, image processing unit or other electronic components. For such applications, the substrate with the metallized holes therein is often referred to as an "interposer". Glass has a number of advantageous properties compared to currently used interlayer materials, such as fiber reinforced polymers or silicon. Glass can be formed into thin, smooth, large sheets without polishing, which has higher hardness and greater dimensional stability than organic alternatives, which is a much better electrical insulator than silicon, which has better dimensional (thermal and rigid) stability than organic options, and which can be tuned to different coefficients of thermal expansion to control stack warpage in integrated circuits.

Various hole forming methods can be used to form holes in glass, such as hot pressing, photolithography of optically processable glass, arc drilling, powder spraying, and various laser drilling methods. Using any of these techniques, the challenge is generally to form pores of sufficiently high quality (low cracking, adequate size or roundness) around at a sufficiently high rate (pores/second), which ultimately impacts cost. For example, hot pressing of glass can make it difficult to form holes of sufficiently small (less than or equal to about 100 microns) size, arc drilling can be difficult to perform at tight hole pitches (i.e., hole-to-hole distances of less than about 50 microns), laser drilling of holes using beam drilling can be slow (e.g., about 1 hole/second), and laser-based and optically-processable glasses can have large initial capital costs.

Laser drilling methods using UV nanosecond lasers have been shown to produce particularly high quality holes. Pilot holes of about 10 microns in diameter are prepared with a laser by using multiple (e.g., hundreds) laser pulses per hole, then acid etching is used to enlarge the hole and achieve the target size. The holes are then metallized, redistribution layers are added to fan out the electrical signals, and the part is cut into smaller pieces to form the functional insertion layer. However, laser drilling can be a time consuming process, and uses percussive drilling (i.e., one pulse after another at the same location), which can require hundreds of pulses to drill individual holes to the desired depth. Because the capital cost of precision laser drilling platforms can be high (approaching $ 100 million/machine), hole formation speed is a critical parameter in overall interposer manufacturing cost.

Accordingly, there is a need for a method of laser drilling materials, such as glass, that minimizes or eliminates the above-mentioned problems.

SUMMARY

Embodiments described herein relate to a method of forming damage tracks (also referred to as pilot holes) at an extremely fast rate. By utilizing a special optical delivery system and picosecond pulsed laser, damage tracks/guide holes can be drilled in glass or other transparent materials and as few as a single laser pulse is required to form each damage track/guide hole. This process achieves damage track/pilot hole drilling rates that are easily 100 times faster than those achievable using the nanosecond laser drilling process described above. However, the initial damage tracks/pilot holes are typically too small to fill with conductive material and are often not continuous. Such damage tracks/guiding holes are therefore not suitable for insertion of layers or electrical vias themselves. By combining the above process with a subsequent acid etching step, the damage tracks or guide holes can then be enlarged in a highly parallel process to the hole size available for the insertion layer. This combined process produces holes in the glass with the appropriate size (on the order of less than 20-tens of microns), profile and quality for the interleaf layers at much lower cost/parts than other methods.

In one embodiment, a method of laser drilling or forming vias in a substantially transparent material includes focusing a pulsed laser beam into a laser beam focal line oriented along a beam propagation direction and directed into the material, the laser beam focal line producing induced absorption within the material, the induced absorption producing a damage track along the laser beam focal line within the material, and translating the material and the laser beam relative to each other, whereby the laser forms a plurality of damage tracks. The method further comprises etching the material in an acid solution to produce pores having a diameter greater than 1 micron by enlarging lines of defects in the material. The etch rate may be a rate of less than about 10 microns/minute, such as a rate of less than about 5 microns/minute, or a rate of less than about 2 microns/minute. The theler modulus of the etching process may be less than or equal to 2.

In some embodiments, the pulse duration may be greater than about 1 picosecond to less than about 100 picoseconds, such as greater than about 5 picoseconds and less than about 20 picoseconds, and the repetition rate may be between about 1kHz and 4MHz, such as between about 10kHz and 650 kHz. In addition to a single pulse at the above-described repetition rate, the pulses may be generated in bursts of two or more pulses (e.g., 3 pulses, 4 pulses, 5 pulses, or more) separated by a duration of about 1 nanosecond to about 50 nanoseconds (e.g., 10 to 30 nanoseconds, such as about 20 nanoseconds ± 2 nanoseconds) and an energy of at least 40 microjoules per burst, and the burst repetition frequency may be about 1kHz to about 200 kHz. The pulsed laser beam may have a wavelength selected so that the material is substantially transparent at that wavelength. The average laser energy/pulse burst measured at the material may be greater than 40 microjoules per millimeter of material thickness, such as 40 microjoules per millimeter-1000 microjoules per millimeter, or 100 microjoules per millimeter-650 microjoules per millimeter. The pulse group energy density of the pulsed laser beam can be between 25 microjoules/millimeter line focus and 125 microjoules/millimeter line focus. The pulsed laser beam can produce at least 500 damage tracks/second, at least 1,000 damage tracks/second, or at least 5,000 damage tracks/second. Damage tracks can be prepared in a non-periodic pattern.

The laser beam focal line may be formed by using a Bessel beam or a Gauss-Bessel beam. The focal lines may be generated using axicon (axicon). The laser beam focal line can have a length of about 0.1mm to about 10mm, e.g., about 1mm, about 2mm, about 3mm, about 4mm, about 5mm, about 6mm, about 7mm, about 8mm, or about 9mm, or a length of about 0.1mm to about 1mm, and an average spot diameter of about 0.1 microns to about 5 microns. The via diameters may be 5 microns to 100 microns, respectively. The damage tracks may each have a diameter of less than or equal to about 5 microns. In some embodiments, the material may be a stack of glass sheets. The spacing of the pores may be 50 microns to 500 microns, or 10 microns to 50 microns. Translating the material and the laser beam relative to each other can include translating the glass sheet using a series of linear stages, or translating the laser beam using a linear stage, a resonant scanning mirror scanner, a galvanometer (galvo) mirror scanner, a piezo-electrically adjustable mirror, or an acousto-optic beam deflector. The method may further comprise coating the interior glass surface at the via with a conductor to create electrical conductivity between the top and bottom of the via, or coating the interior glass surface at the via to facilitate attachment of the biomolecule. The material may be transparent to at least one wavelength of 390nm-700nm and/or at least 70% transmissive to at least one wavelength of 390nm-700 nm. The material may be glass, fused quartz, or a stack of glass sheets.

In some embodiments, the plurality of through-holes have a diameter of 20 microns or less, a spacing between adjacent through-holes is 10 microns or more, the plurality of through-holes comprises openings in the first surface, openings in the second surface, and a waist between the openings in the first surface and the openings in the second surface, the waist diameter is at least 50% of the diameter of the openings in the first surface or the openings in the second surface, and a difference between the diameter of the openings in the first surface and the diameter of the openings in the second surface is 3 microns or less. Other embodiments include glass articles made according to the methods described above and in the detailed description.

In another embodiment, a glass article comprises a substrate having a plurality of damage tracks, wherein the damage tracks have a diameter of less than 5 microns, a spacing between adjacent holes is at least 20 microns, and an aspect ratio of 20:1 or greater. The damage track diameter may be less than 1 micron.

In yet another embodiment, a glass article comprises a stack of glass substrates having a plurality of holes formed through the stack, wherein the holes extend through each glass substrate, and wherein the holes have a diameter of about 1 micron to about 100 microns and a hole-to-hole spacing of about 25 to 1000 microns. The glass article can comprise at least two glass substrates separated by an air gap greater than 10 microns.

In yet another embodiment, a substantially transparent article comprises a multilayer stack of materials that are substantially transparent to wavelengths from about 200nm to about 2000nm, the multilayer stack having a plurality of apertures formed through a plurality of layers of the stack. The diameter of the pores is 1-100 microns and the pore-to-pore spacing is 25-1000 microns. The multilayer stack can comprise any one or more of a) a plurality of glass layers and at least one polymer layer disposed between the glass layers, b) at least two glass layers having different compositions, or c) at least one glass layer and at least one non-glass inorganic layer.

In yet another embodiment, a method of forming a via in a material comprises forming a plurality of damage tracks in the material by focusing a pulsed laser beam into a laser beam focal line oriented along a beam propagation direction and directing the laser beam focal line into the material, wherein the damage tracks are 5 microns or less in diameter, and etching the material in an acid solution to enlarge the plurality of defect lines to produce a plurality of vias in the material, wherein the etched theler modulus is less than or equal to 2. The material may be transparent to at least one wavelength of 390nm-700nm and/or may transmit at least 70% of at least one wavelength of 390nm-700 nm. The method may further comprise mechanically agitating the acid solution during the etching. The acid solution may comprise a surfactant. The plurality of vias can have a diameter of 20 microns or less and a spacing between adjacent vias is at least 10 microns. The plurality of through-holes includes an opening in the first surface, an opening in the second surface, and a waist located between the opening in the first surface and the opening in the second surface, the waist diameter being at least 50% of a diameter of the opening in the first surface or the opening in the second surface, and a difference between the diameter of the opening in the first surface and the diameter of the opening in the second surface being 3 microns or less.

At one endIn some embodiments, an article includes a substrate having a plurality of through-holes extending continuously from a first surface of the substrate to a second surface of the substrate, wherein the substrate is transparent to at least one wavelength in the range of 390nm to 700nm, the plurality of through-holes having a diameter of 20 microns or less, the plurality of through-holes comprising openings in the first surface, openings in the second surface, and a waist between the openings in the first surface and the openings in the second surface, the waist having a diameter that is at least 50% of the diameter of the openings in the first surface or the openings in the second surface, and a difference between the diameter of the openings in the first surface and the diameter of the openings in the second surface is 3 microns or less. The plurality of vias may have a diameter of greater than 5 microns, 15 microns or less, or 10 microns or less. The waist diameter is at least 70%, at least 75%, or at least 80% of the diameter of the opening in the first surface or the opening in the second surface. The substrate may be fused quartz, glass, or chemically strengthened glass. The substrate may have a thickness of 1mm or less, or a thickness of 20 microns to 200 microns. The density of the through holes can be 5 through holes/mm²-50 through holes/mm². The aspect ratio of the through-hole may be 5:1 to 20: 1. The vias may have a non-periodic pattern. The via contains a conductive material.

Embodiments described herein provide a number of advantages, including the formation of hole/damage tracks using as few as a single laser pulse or a single pulse burst, which results in a much faster rate of hole or hole/damage track formation than conventional shock drilling laser methods. The hole/damage track drilling described herein is limited only by the repetition rate of the laser and the speed at which the laser beam moves to the next drilling location. Drilling speeds of several hundred holes/second are readily available and, depending on the land and hole pattern density used, drilling rates of greater than 10,000 holes/second can be achieved. Furthermore, this process can drill multiple parts simultaneously (in a stack), which further increases system throughput.

Because of the line focusing optics, the diameter of the laser drilled hole/damage track is extremely small (e.g., about 1 micron), which is much smaller than the ablated hole size (typically greater than about 10 microns) that can be obtained using a Gaussian optical beam.

The use of acid etching allows the formation of vias of a size that can be used for metallization or other chemical coatings. In the parallel process, all guide holes/damage tracks are enlarged to the target diameter in parallel, which is much faster than drilling holes into larger holes using a laser by using further laser exposure.

By passivating any microcracks or damage caused by the laser, the acid etch forms a stronger part than if the laser were used alone.

Brief description of the drawings

The foregoing will be apparent from the following more particular description of example embodiments as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments.

FIG. 1 schematically shows an embodiment of an optical assembly for laser drilling.

FIG. 2A shows an optical assembly for laser machining according to one embodiment.

Figures 2B-1 to 2B-4 show various possibilities for processing a substrate by differently positioning the laser beam focal line relative to the substrate.

Fig. 3 shows a second embodiment of an optical assembly for laser machining.

Fig. 4A and 4B show a third embodiment of an optical assembly for laser machining.

The graph of fig. 5 shows the laser emission (intensity) of an exemplary picosecond laser as a function of time.

FIGS. 6A and 6B are scanning electron micrographs of features formed by laser drilling, taken together

And (3) preparing the glass.

Fig. 7 is a microscopic image of a typical damage track, perforation or defect line (the three terms are used interchangeably herein), which is a side view without etching. The marks made through the glass are typically not fully opened-i.e., the area material is removed, but complete vias need not be formed.

Fig. 8 is a microscopic side view without damage tracks or perforations by acid etching, at a magnification greater than that of the micrograph shown in fig. 7.

Fig. 9 is a microscopic image of a top view of a typical damage track or hole without acid etching.

Fig. 10 is a scanning electron micrograph of a hole prepared using processing conditions that form significant microcracking by using a shorter focal length objective lens (f ═ 30mm) that forms a shorter focal line (0.5 mm) and thus a high energy density in the defect line.

FIG. 11 is a scanning electron micrograph of a hole that does not penetrate the full thickness of the part, which can be used to make a blind hole.

Fig. 12A and 12B are scanning electron micrographs of an entrance aperture (laser incident side) after etching and an exit aperture (laser exit side) after acid etching, respectively.

Fig. 13 is an image after etching effected by microcracking. The microcracks have been acid etched into elongated features.

The photo of fig. 14 shows a side view of the hole after acid etching. The sample was cut into small pieces to show the cross-section. The bright areas are glass and the dark areas are holes.

The optical photograph of fig. 15 shows a side view of the holes after acid etching, but at a higher magnification than the optical photograph shown in fig. 14.

The graphs of fig. 16A-16C show the number of pores at the top (fig. 16A), bottom (fig. 16B), and at the waist (fig. 16C) as a function of diameter, which shows pore size statistics for about 10,000 pores after etching.

The graphs of fig. 17A-17C show the number of holes at the top (17A), bottom (17B), and at the waist (17C) as a function of diameter, which shows roundness statistics after etching. Roundness is the maximum diameter-minimum diameter of a given hole. The data indicates that all holes are free of significant cracks/gaps that will be etched into significant non-round shapes.

Fig. 18A-18C are optical photographs of a radial crack prior to etching (fig. 18A), and a larger magnification of the array of entrance apertures (fig. 18B and 18C).

Fig. 19A-19C are photomicrographs of the holes before etching, showing a top view (fig. 18A), a bottom view (fig. 18B), and a side view (fig. 18C).

Fig. 20A-20E are optical photographs of a top view of a hole after acid etching at 55% laser power (fig. 20A), 65% laser power (fig. 20B), 75% laser power (fig. 20C), 85% laser power (fig. 20D), and 100% laser power (fig. 20E).

Fig. 21A-21E are photomicrographs of a bottom view of the holes after acid etching at 55% laser power (fig. 21A), 65% laser power (fig. 21B), 75% laser power (fig. 21C), 85% laser power (fig. 21D), and 100% laser power (fig. 21E).

FIGS. 22A-22C are photomicrographs of a top view of the holes after acid etching-FIG. 22A: 100 micrometer holes in a 150X150 array with a pitch of 200 micrometers; 22B and22C A300X 300 array of 50 micron holes with a pitch of 100 microns showing (FIG. 22C) some cracked holes and chipped holes.

Figures 23A-23C are graphs showing the number of wells as a function of diameter for samples having a 100x100 array of wells, showing results for the top (figure 23A), bottom (figure 23B), and waist (figure 23C) of the samples.

Figures 24A-24C are graphs showing the number of wells of a sample with a 100x100 array of wells as a function of roundness, which shows results for the top (figure 24A), bottom (figure 24B), and waist (figure 24C) of the sample.

Figures 25A-25C are graphs showing the number of wells as a function of diameter for samples having a 100x100 array of wells, showing results for the top (figure 25A), bottom (figure 25B), and waist (figure 25C) of the second sample.

Figures 26A-26C are graphs showing the number of wells as a function of roundness for samples having a 100x100 array of wells, showing results for the top (figure 26A), bottom (figure 26B), and waist (figure 26C) of the second sample.

Fig. 27A-27C and 28A-28C are photomicrographs of 30 micrometer and 50 micrometer holes, respectively, made using 100% laser power after acid etching, showing top (fig. 27A,28A) side (fig. 27B,28B), and bottom (fig. 27C,28C) views.

Fig. 29A-29C and 30A-30C are photomicrographs of 75 micrometer and 100 micrometer holes, respectively, made using 100% laser power after acid etching, showing top (fig. 29A,30A) side (fig. 29B,30B), and bottom (fig. 29C,30C) views.

Fig. 31A-31C and 32A-32C are photomicrographs of 30 micrometer and 50 micrometer holes, respectively, made using 85% laser power after acid etching, showing top (fig. 31A,32A) side (fig. 31B,32B), and bottom (fig. 31C,32C) views.

Fig. 33A-33C and 34A-34C are photomicrographs of 75 micrometer and 100 micrometer holes, respectively, made using 85% laser power after acid etching, showing top (fig. 33A,34A), side (fig. 33B,34B), and bottom (fig. 33C,34C) views.

Fig. 35A-35C and 36A-36C are optical photographs of 30 micron and 50 micron holes prepared using 75% laser power, respectively, after acid etching, showing top (fig. 35A,36A), side (fig. 35B,36B), and bottom (fig. 35C,36C) views.

Fig. 37A-37C and 38A-38C are photomicrographs of 75 micrometer and 100 micrometer holes, respectively, made using 75% laser power after acid etching, showing top (fig. 37A,38A), side (fig. 37B,38B), and bottom (fig. 37C,38C) views.

Fig. 39A-39C and 40A-40C are photomicrographs of 30 micrometer and 50 micrometer holes, respectively, made using a 65% laser power after acid etching, showing top (fig. 39A,40A), side (fig. 39B,40B), and bottom (fig. 39C,40C) views.

Fig. 41A-41C and 42A-42C are photomicrographs of 75 micrometer and 100 micrometer holes, respectively, made using a 65% laser power after acid etching, showing top (fig. 41A,42A), side (fig. 41B,42B), and bottom (fig. 41C,42C) views.

Fig. 43A-43C and 44A-44C are photomicrographs of 30 micrometer and 50 micrometer holes, respectively, made using 55% laser power after acid etching, showing top (fig. 43A,44A) side (fig. 43B,44B), and bottom (fig. 43C,44C) views.

Fig. 45A-45C and 46A-46C are photomicrographs of 75 micrometer and 100 micrometer holes, respectively, made using 55% laser power after acid etching, showing top (fig. 45A,46A), side (fig. 45B,46B), and bottom (fig. 45C,46C) views.

FIG. 47 showsShowing 150 microns extending through a 3-up stack

Focal lines of the glass sheet.

FIG. 48 is an optical photograph prior to acid etching showing a side view of a stack of two 300 micron thick EXG glasses drilled with damage tracks.

Fig. 49 is a photomicrograph after acid etching showing a side view of the same stack as shown in fig. 48 after acid etching.

Fig. 50 is a photomicrograph after acid etching showing a top view of the same stack as shown in fig. 48 after acid etching.

Fig. 51A and 51B show thesubstrate 1000 after laser drilling and after acid etching, respectively.

FIG. 52 shows the Therler (Thiele) modulus of the etching system as a function of the expected waist diameter in percent relative to the top and bottom opening diameters.

FIG. 53 is a plot of Theiler modulus of an etching system as a function of radius of a damage track.

FIG. 54 is a plot of the Theiler modulus of the etching system as a function of the half thickness of the glass substrate.

FIG. 55 is a graph of the Theiler modulus versus effective diffusion coefficient (D) for an etch system_{Is effective}) And (3) plotting the changes.

FIG. 56 is a plot of Theiler modulus for an etching system as a function of acid concentration in volume percent and shows the combined effect of varying the effective diffusion coefficient and acid concentration on the Theiler modulus.

Fig. 57 is an optical photograph of a side view of a glass part after acid etching.

DETAILED DESCRIPTIONS

Example embodiments will be described below.

The following embodiments utilize shorter (e.g., 10) with optical systems^-10-10^-15Second) pulsed laser forming a line focus system to form defect lines, damage tracks or holes in a piece of material that is substantially transparent to the laser wavelength, e.g. glass, fused quartz, glass, quartz,Synthetic quartz, glass-ceramics, crystalline materials such as sapphire, or laminated layers of such materials (e.g., coated glass). Producing line focusing can be done by emitting a Gaussian laser beam into an axicon lens, in this case, forming a beam profile with what is called a Gauss-Bessel beam. Such a beam diffracts much more slowly than a Gaussian beam (e.g., it can maintain a single micron spot size in the range of hundreds of microns or millimeters as opposed to tens of microns or less for a Gaussian beam). Thus, the depth of focus or length of the strong interaction with the material will be much larger than if only a Gaussian beam were used. Other forms or slowly diffractive or non-diffractive beams, such as Airy beams, may also be used. The material or article is substantially transparent to the laser wavelength when the absorption is less than about 10%, preferably less than about 1%, per millimeter of material depth at the laser wavelength. In some embodiments, the material may also be transparent to at least one wavelength in the range of about 390nm to about 700 nm. The use of a high intensity laser and line focus allows each laser pulse to simultaneously damage, ablate, or otherwise alter (e.g., 100-. Such marks can easily extend through the entire thickness of the glass part. Thus, even a single pulse or burst (burst) can form a complete "pilot hole" or a sharp damage track without the need for percussion drilling.

The cross-sectional dimensions of the pilot holes/damage tracks are very small (a single micron or less) but rather long-i.e. they have a high aspect ratio. The part is then acid etched to obtain a final pore size-e.g., a diameter of about 30 microns or less, about 25 microns or less, about 20 microns or less, about 15 microns or less, about 10 microns or less, about 5 to about 10 microns, about 5 to about 15 microns, about 5 to about 20 microns, about 5 to about 25 microns, about 5 to about 30 microns, or up to several tens of microns, depending on the requirements of the intended application. In some embodiments, the etching may be performed such that the theler modulus of the etching process is about 3 or less, about 2.5 or less, about 2 or less, about 1.5 or less, about 1 or less, or about 0.5 or less. After etching, the glass surface is slightly textured by imperfect uniformity during etching-while the interior of the etched holes is somewhat smooth and may have some ultrafine grain texture, which is visible under a microscope or scanning electron microscope. In some embodiments, the substrate can have a plurality of through holes extending continuously from a first surface of the substrate to a second surface of the substrate, wherein the substrate is transparent to at least one wavelength in the range of 390nm to 700nm, the plurality of through holes having a diameter of 20 microns or less, the plurality of through holes comprising openings in the first surface, openings in the second surface, and a waist between the openings in the first surface and the openings in the second surface, the waist having a diameter that is at least 50% of the diameter of the openings in the first surface or the openings in the second surface, and the difference between the diameter of the openings in the first surface and the diameter of the openings in the second surface being 3 microns or less.

The holes may then be coated and/or filled with a conductive material (e.g., by metallization) to form an insert part made of a transparent material. The metal or conductive material may be, for example, copper, aluminum, gold, silver, lead, tin, indium tin oxide, or combinations or alloys thereof. The process for the metallization inside the hole may be, for example, electroplating, electroless plating, physical vapor deposition, or other vapor coating methods. The pores may also be coated with a catalytic material, such as platinum, palladium, titanium dioxide, or other materials that promote chemical reactions within the pores. Alternatively, the pores may be coated with other chemical functionalisation to alter surface wetting properties or to enable attachment of biomolecules and for biochemical analysis. Such chemical functionalization may be silanization of the glass surface of the pores and/or additional attachment of specific proteins, antibodies or other biospecific molecules designed to facilitate attachment of biomolecules for desired applications.

In one embodiment, a method of laser drilling a material includes focusing a pulsed laser beam into a laser beam focal line oriented along a beam propagation direction and directed into the material, the laser beam having an average laser pulse group energy measured at the material greater than about 50 microjoules per millimeter of thickness of the material being processed, the laser beam having a pulse group energy density of from about 25 microjoules per millimeter of line focus to about 125 microjoules per millimeter of line focus, the laser beam having a pulse duration of less than about 100 picoseconds and a repetition rate of from about 1kHz to about 4 MHz. The length of the line focus can be determined by: the intensity is the distance between two points at half the maximum intensity on the optical axis. The laser beam focal line produces an induced absorption within the material, the induced absorption forming a hole within the material along the laser beam focal line. The method also includes translating the material and the laser beam relative to each other, thereby laser drilling a plurality of holes (or damage tracks) within the material at a rate of: greater than about 50 pores/second, greater than about 100 pores/second, greater than about 500 pores/second, greater than about 1,000 pores/second, greater than about 2,000 pores/second, greater than about 3,000 pores/second, greater than about 4,000 pores/second, greater than about 5,000 pores/second, greater than about 6,000 pores/second, greater than about 7,000 pores/second, greater than about 8,000 pores/second, greater than about 9,000 pores/second, greater than about 10,000 pores/second, greater than about 25,000 pores/second, greater than about 50,000 pores/second, greater than about 75,000 pores/second, or greater than about 100,000 pores/second, depending on the desired pattern of pores/damage tracks. The method further comprises etching the material in an acid solution at a rate of less than about 5 microns/minute, for example at a rate of about 2 microns/minute, thereby enlarging pores in the material.

In some embodiments, the pulse duration may be greater than about 5 picoseconds to less than about 100 picoseconds, and the repetition rate may be between about 1kHz and 4 MHz. The pulses may be generated in bursts of at least two pulses separated by a duration of between about 1 nanosecond and about 50 nanoseconds, such as between 10 and 30 nanoseconds, for example about 20 nanoseconds ± 2 nanoseconds, and the burst repetition frequency may be between about 1kHz and about 4 MHz. The pulsed laser beam may have a wavelength selected so that the material is substantially transparent at that wavelength. This wavelength may be, for example, 1064,532,355, or 266 nanometers. In some embodiments, the burst repetition frequency can be from about 1kHz to about 4MHz, from about 10kHz to about 650kHz, about 10kHz or greater, or about 100kHz or greater.

The laser beam focal line may have a length of about 0.1mm to about 10mm, or a length of about 0.1mm to about 1mm, and an average spot diameter of about 0.1 microns to about 5 microns. The spot diameter D of a Bessel beam can be written as D ═ 2.4048 λ)/(2 π B, where λ is the laser beam wavelength and B is a function of the cone angle of the beam.

Laser and optical system:

for cutting transparent substrates, in particular glass, a method was developed which uses a 1064nm picosecond laser and optics forming a line-shaped focused beam, so that damage lines or damage tracks are formed in the substrate. This is described in detail below and is described in us patent application No. 61/752,489 filed on 15/1/2013, which is a priority application for us patent application No. 14/154,525 (us patent application publication No. 2014/0199519) filed on 14/1/2014, which is incorporated herein by reference in its entirety. In this context, a damage track formed by a laser may interchangeably refer to a hole, a pilot hole, a defective line, or a perforation. The method of cutting the transparent substrate may also be applied to form damage tracks, which are subsequently magnified by an etching process, as described below.

Fig. 1 provides a schematic diagram of one version of the concept in which light rays from a laser 3 (not shown) are focused into apattern 2b having a linear shape, parallel to the optical axis of the system, using axiconoptical elements 10 andother lenses 11 and 12. Thesubstrate 1 is arranged such that it is within the linear focus. With a line focus in the range of about 1mm and a picosecond laser (about 200 microjoules per pulse burst measured at the material) producing an output power of greater than or equal to about 20W at a repetition rate of 100kHz, the optical intensity in theline region 2b can then easily be high enough to form a non-linear absorption in the material. The average laser pulse burst energy of the pulsed laser beam measured at the material may be greater than 40 microjoules per millimeter of material thickness. The average laser burst energy used may be as high as 2500 microjoules per mm of material thickness, for example 100-. This "average laser energy" may also be referred to as an average, per pulse burst, linear energy density, or average energy per laser pulse burst per millimeter of material thickness. In some embodiments, the burst energy density can be from about 25 microjoules/mm line focus to about 125 microjoules/mm line focus, or from about 75 microjoules/mm line focus to about 125 microjoules/mm line focus. Creating areas of damaged, ablated, vaporized or otherwise altered material that approximately follow a linear region of high intensity.

A method of laser processing a material includes focusing apulsed laser beam 2 into a laser beamfocal line 2b oriented along a beam propagation direction. As shown in fig. 2A, a laser 3 (not shown) emits alaser beam 2 having a portion 2A incident on theoptical assembly 6. On the output side, along the beam direction over a defined expansion range (length l of the focal line), theoptical assembly 6 converts the incident laser beam into an extended (extended) laser beamfocal line 2 b. Theflat substrate 1 is disposed in the beam path so as to at least partially overlap the laser beamfocal line 2b of thelaser beam 2. Thus, the laser beam focal line is directed into the substrate.Reference numeral 1a denotes a surface of the flat substrate facing theoptical assembly 6 or the laser, and reference numeral 1b denotes a reverse surface of thesubstrate 1, respectively. The substrate or material thickness (in this embodiment, measured perpendicular to theplanes 1a and 1b, i.e. perpendicular to the substrate plane) is marked with d. For example, the substrate or material may be a glass article that is substantially transparent to the wavelength of thelaser beam 2.

The substrate 1 (or material or glass article) is aligned perpendicular to the longitudinal beam axis and thus behind the samefocal line 2b produced by the optical assembly 6 (substrate perpendicular to the plane of the drawing). The focal lines are oriented or aligned along the beam direction, and the substrate is positioned relative to thefocal lines 2b such that thefocal lines 2b start before thesurface 1a of the substrate and end before thesurface 1b of the substrate, i.e. thefocal lines 2b terminate within the substrate and do not extend beyond thesurface 1 b. In the overlapping area of the laser beamfocal line 2b and thesubstrate 1, i.e. in the substrate material covered by thefocal line 2b, an extended laser beamfocal line 2b is generated (assuming that a suitable laser intensity is formed along the laser beamfocal line 2b, which intensity is ensured by focusing of thelaser beam 2 over a length i portion, i.e. a line-shaped focusing of the length i) an extendedportion 2c (aligned along the longitudinal beam direction) and an induced absorption is generated in the substrate material along theextended portion 2 c. The induced absorption forms defect lines in the substrate material along theportion 2 c. Defect lines are microscopic (e.g., >100nm and <0.5 microns in diameter) elongated "holes" (also known as perforations, damage tracks, or defect lines) in a substantially transparent material, substrate, or workpiece, which are created by using a single high-energy pulse burst pulse. For example, a single perforation may be formed at a rate of several hundred kilohertz (hundreds of thousands of perforations per second). These perforations can be placed adjacent to each other (spatial separation varying from sub-micron to many microns as desired) by means of relative movement between the source and the material. Such spatial separation (pitch) may be selected to facilitate separation of the materials or workpieces. In some embodiments, the defect line/damage track is a "via," which is a hole or open channel that extends substantially from the top to the bottom of the transparent material. In other embodiments, the damage tracks are not true "through holes" because there are particles of material that block the damage track path. Thus, while the damage track may extend from the top surface to the bottom surface of the material, in some embodiments it is not a continuous hole or channel because the material particles block the path. The defect line/damage track formation is not local but over the full length of the absorption-inducingextensions 2 c. The length of theportion 2c (which corresponds to the length of the laser beamfocal line 2b overlapping the substrate 1) is marked with reference L. The average diameter or extent of theportion inducing absorption 2c (or the portion of the material of thesubstrate 1 that is subject to defect line formation) is marked with the reference D. This average range D substantially corresponds to the average diameter δ of the laser beamfocal line 2b, i.e., an average spot diameter of about 0.1 microns to about 5 microns.

Thus, microscopic (i.e., <2 microns and >100nm in diameter, and in some embodiments <0.5 microns and >100nm) elongated "holes" (also referred to as perforations, damage tracks, or defect lines, as described above) can be formed in transparent materials using a single high-energy pulse burst pulse. These individual perforations may be formed at a rate of several hundred kilohertz (e.g., several hundred thousand perforations per second). Thus, the perforations can be placed at any desired location within the workpiece by relative movement between the source and the material. In some embodiments, the defect line/damage track is a "via," which is a hole or open channel that extends from the top to the bottom of the transparent material. In some embodiments, the defect line/damage track may not be a continuous channel and may be blocked or partially blocked by portions or segments of solid material (e.g., glass). As defined herein, the internal diameter of a defect line/damage track is the internal diameter of an open channel or air hole. For example, in the embodiments described herein, the internal diameter of the defect line/damage track is <500nm, such as ≦ 400nm, or ≦ 300 nm. In the embodiments described herein, the disturbed or altered regions of material surrounding the pores (e.g., densified, fused, or otherwise altered) preferably have a diameter of <50 microns (e.g., <10 microns).

Because of the induced absorption along thefocal line 2b, the substrate material (transparent to the wavelength λ of the laser beam 2) is heated, which results from the non-linear effects associated with the high intensity of the laser beam within thefocal line 2 b. It is shown that the heated substrate material eventually expands, whereby the corresponding induced tension leads to the formation of micro-cracks, and the tension is maximal at thesurface 1 a.

The selection of the laser source is predicted based on the ability to form multiphoton absorption (MPA) in the transparent material. MPA is the simultaneous absorption of two or more photons of the same or different frequencies, thereby exciting a molecule from one state (usually the ground state) to a higher energy electronic state (possibly leading to ionization). The energy difference between the lower and upper states of the molecule involved may be equal to the sum of the energies of the two or more photons. MPA, also known as induced absorption, can be a secondary, tertiary, or higher order process, e.g., it is orders of magnitude weaker than linear absorption. MPA differs from linear absorption in that, for example, the intensity of the induced absorption can be proportional to the square, cube, or higher power (power) of the light intensity, rather than the light intensity itself. Thus, MPA is a nonlinear optical process.

Representativeoptical assemblies 6 that can be used to generate thefocal line 2b, and representative optical devices in which these optical assemblies can be applied, are described below. All assemblies or devices are based on the above, so that the same reference numerals are used for the same components or features or functionally equivalent ones. Therefore, only the differences will be described below.

To ensure high quality drilling (involving obtaining high fracture strength, geometric accuracy, forming a strong path for the etchant, hole topography, and avoiding micro-cracking), a single focal line disposed on the substrate surface should be generated using an optical assembly as described below (hereinafter, the optical assembly is also alternatively referred to as a laser optic). In order to obtain a small spot size, e.g. 0.5-2 microns, at a given wavelength λ of the laser light 3 (interacting with thesubstrate 1 material), certain requirements must generally be imposed on the numerical aperture of thelaser optics 6.

On the other hand, to obtain the required numerical aperture, the optics must be set to the opening required for a given focal length, according to the known abbe's formula (n.a.: nsin (θ), n: the refractive index of the glass or other material being processed, θ: half of the aperture angle, and θ ═ arctan (D/2 f); D: aperture, f: focal length). On the other hand, the laser beam must illuminate optics up to the required aperture, which is typically achieved by using beam expansion of a broadening telescope between the laser and the focusing optics.

The spot size variation should not be too large for uniform interaction along the focal line. This can be ensured, for example, by the following (see the embodiments below): the focusing optics are illuminated only in a small circular area, so that the beam opening and thus the percentage of the numerical aperture changes only slightly.

According to fig. 2A (cross section perpendicular to the substrate plane and at the central beam in the laser beam cluster of thelaser radiation 2; here thelaser beam 2 is also incident perpendicularly to the substrate plane, i.e. the angle of incidence is 0 °, so that thefocal line 2b or the extension of the inducedabsorption 2c is parallel to the substrate normal), the laser radiation 2A emitted by thelaser 3 is first directed onto acircular aperture 8, which is completely opaque to the laser radiation used. Theaperture 8 is oriented perpendicular to the longitudinal beam axis and centered on the central beam of the illustratedcluster 2 a. The diameter of theaperture 8 is chosen such that the cluster or central beam (here marked with 2 aZ) near the center of thecluster 2a strikes the aperture and is completely absorbed by it. Since the aperture size is reduced compared to the beam diameter, only the beam (marginal ray, here labeled 2 aR) at the outer circumferential extent of thebeam cluster 2a is not absorbed, but passes sideways through theaperture 8 and strikes the marginal areas of the focusing optics of theoptical assembly 6, which focusing optics of theoptical assembly 6 are designed in this embodiment as a spherically cut,biconvex lens 7.

As shown in fig. 2A, the laser beamfocal line 2b is not a single focal point of the laser beam, but a series of focal points for different rays in the laser beam.The series of focal points form an elongated focal line having a defined length (shown in fig. 2A as the length l of the laser beamfocal line 2 b). Thelens 7 is centered on the central beam and is designed as a non-collimating, double convex focusing lens in the form of a commonly used spherical cut lens. Such spherical aberration of the lens may be preferred. Alternatively, an aspherical or multi-lens system deviating from an ideal collimating system may also be used, which does not form an ideal focal point but a different elongated focal line of defined length (i.e. a lens or system without a single focal point). The area of the lens is thus focused along thefocal line 2b, subject to the distance from the center of the lens. The diameter of thediaphragm 8 across the beam direction is about 90% of the diameter of the cluster (from the beam intensity down to 1/e of maximum intensity)²The required distance) and is about 75% of the diameter of the lens of theoptical assembly 6. Therefore, thefocal line 2b of thespherical lens 7 is calibrated using the non-chromatic aberration generated by blocking the beam cluster at the center. Fig. 2A shows a cross-section in a plane through the central beam and when the illustrated beam is rotated around thefocal line 2b, the complete three-dimensional cluster is visible.

One potential disadvantage of such focal lines is that the conditions (spot size, laser intensity) may vary along the focal line (and along the desired depth in the material), and thus the desired type of interaction (no melting, induced absorption, thermoplastic deformation until crack formation) may occur only in selected portions of the focal line. This in turn means that it is possible that only a part of the incident laser light is absorbed by the substrate material in the desired manner. As such, the efficiency of the process (the required average laser power for the required separation speed) may be reduced, and the laser may also be transmitted into unwanted areas (parts or layers bonded to the substrate or fixtures holding the substrate) and interact with them in a disadvantageous manner (e.g., heating, diffusion, absorption, unwanted modification).

Fig. 2B-1-4 show (not only for the optical assembly in fig. 2A, but basically for any other applicable optical assembly 6) that the position of the laser beam focal line 2B can be controlled by: theoptical assembly 6 is suitably arranged and/or aligned with respect to thesubstrate 1 and the parameters of theoptical assembly 6 are suitably selected. As shown in FIG. 2B-1, the length l of the focal line 2B can be adjusted so that it exceeds the substrate thickness d (here by a factor of 2). If thesubstrate 1 is arranged (viewed in the longitudinal beam direction) centrally to thefocal line 2b, a continuation of the inducedabsorption 2c is produced over the entire substrate thickness. For example, the length l of the laser beamfocal line 2b may be from about 0.01mm to about 100mm or from about 0.1mm to about 10 mm. For example, various embodiments may be configured to include a length l of about 0.1mm,0.2mm,0.3mm,0.4mm,0.5mm,0.7mm,1mm, 2mm,3mm, or 5 mm.

In the case shown in fig. 2B-2, a focal line 2B of length l is generated, which more or less corresponds to the substrate thickness d. Because thesubstrate 1 is arranged relative to thelines 2b in such a way that thelines 2b start at a point outside the substrate, the length L of the extended portion of the inducedabsorption 2c (which extends from the substrate surface to a defined substrate depth but does not reach thecounter surface 1b) is smaller than the length L of thefocal line 2 b. Fig. 2B-3 shows a case where the substrate 1 (viewed in a direction perpendicular to the beam direction) is disposed above the starting point of the focal line 2B, so that the length L of the line 2B is larger than the length L of the portion of thesubstrate 1 whereabsorption 2c is induced, similarly to fig. 2B-2. Thus, the focal line starts within the substrate and extends beyond thereverse surface 1 b. Fig. 2B-4 show the case where the focal line length l is smaller than the substrate thickness d, so that-in the case where the substrate is arranged centrally with respect to the focal line and viewed in the direction of incidence-the focal line starts from within the substrate near thesurface 1a and ends within the substrate near the surface 1B (e.g.: 0.75 · d).

It is particularly preferable to set thefocal line 2b in the following manner: at least one of thesurfaces 1a, 1b is covered by a focal line, whereby a portion of the inducedabsorption 2c starts on at least one surface of the substrate. In this way, a substantially ideal cutting or damage track formation can be obtained while avoiding ablation, feathering and granulation at the surface.

Fig. 3 shows another usefuloptical assembly 6. The basic construction is the same as that shown in fig. 2A, so only the differences will be described below. The optical assembly shown is based on optics using an aspherical free surface, resulting in afocal line 2b shaped to form a focal line of a defined length l. For this purpose, an aspherical surface may be used as the optical element of theoptical assembly 6. For example, in fig. 3, so-called tapered prisms are used, which are also referred to as axicons. Axicons are special, conically cut lenses that form a spot source (or convert a laser beam into a ring) on a line along the optical axis. Such an arrangement of axicons is well known in the art; the taper angle in the embodiment is 10 °. The apex of the axicon, here designated byreference numeral 9, is directed towards the direction of incidence and is centered on the beam centre. Since thefocal lines 2b produced by theaxicons 9 start within their interior, the substrate 1 (here aligned perpendicular to the main beam axis) can be arranged in the beam path directly behind theaxicons 9. As shown in fig. 3, thesubstrate 1 can also be moved along the beam direction while still being within the range of thefocal line 2b because of the optical characteristics of the axicon. Thus, the part of the material of thesubstrate 1 that induces theabsorption 2c extends over the entire substrate depth d.

However, the layout shown is limited by: since the area of thefocal line 2b formed byaxicon 9 starts withinaxicon 9, when there is a space betweenaxicon 9 and the substrate or glass composite workpiece material, a significant portion of the laser energy is not focused into the portion of thefocal line 2b located within the material that inducesabsorption 2 c. Further, the length l of thefocal line 2b is related to the beam diameter by the refractive index and the cone angle of theaxicon 9. This is why in the case of thinner materials (in this case a few millimetres) the total focal line is much longer than the thickness of the substrate or glass composite workpiece, which has the effect that most of the laser energy is not focused into the material.

For this purpose it may be necessary to use anoptical assembly 6 comprising both axicons and focusing lenses. Fig. 4A shows such anoptical assembly 6, wherein a first optical element comprising an aspherical free surface designed to form an extended laser beamfocal line 2b is arranged in the beam path of thelaser light 3. In the case shown in fig. 4A, this first optical element is anaxicon 10 with a cone angle of 5 °, which is arranged perpendicularly to the beam direction and centered on thelaser beam 3. The apex of the axicon is oriented towards the beam direction. The second focusing optical element, here a plano-convex lens 11, the curved part of which is oriented towards the axicon, is arranged in the beam direction and at a distance z1 from theaxicon 10. In this case, the distance z1 is about 300mm, which is selected in the following way: the laser radiation formed byaxicon 10 is made incident in a circular manner on the outer radial part oflens 11. On afocal line 2b of defined length (in this case 1.5mm), thelens 11 focuses the circular radiation on the output side at a distance z2 (in this case about 20mm from the lens 11). In this embodiment, the effective focal length of thelens 11 is 25 mm. The circular transformation of the laser beam byaxicon 10 is marked with the reference SR.

FIG. 4B shows in detail the formation of focal lines 2B or inducedabsorption 2c in the material of thesubstrate 1 according to FIG. 4A. The optical characteristics of the twoelements 10, 11 and their arrangement are selected in the following manner: the length l of thefocal line 2b in the beam direction is exactly the same as the thickness d of thesubstrate 1. As a result, thesubstrate 1 needs to be accurately disposed in the beam direction so that the position of the focal line 2B is accurately between the twosurfaces 1a and 1B of thesubstrate 1, as shown in fig. 4B.

It would therefore be preferable if the focal line were formed at a distance from the laser optics, and if a larger portion of the laser radiation was focused to the desired end of the focal line. As described herein, this can be achieved by: the primary focusing element 11 (lens) is illuminated in a circular (annular) manner only on a specific outer radial area, which on the one hand serves to obtain the required numerical aperture and thus the required spot size, whereas on the other hand, after the requiredfocal line 2b, over a very short distance in the center of the spot, the intensity of the diffused circle decreases, since a substantially circular spot is formed. In this way, defect line/damage track formation is stopped within a short distance of the required substrate depth. The combination ofaxicon 10 and focusinglens 11 meets this requirement. Axicons function in two different ways: because ofaxicon 10, a laser spot, which is usually circular, is emitted in the form of a ring to the focusinglens 11, and the non-spherical shape ofaxicon 10 has the following effect: instead of forming the focal line at a focal point in the focal plane, the focal line is formed beyond the focal plane of the lens. The length l of thefocal line 2b can be adjusted by the beam diameter on the axicon. On the other hand, the numerical aperture along the focal line can be adjusted by the axicon-lens distance z1 and by the cone angle of the axicon. In this way, the entire laser energy can be concentrated in the focal line.

If it is desired that the defect line/damage track formation continue to the back of the substrate, circular (annular) illumination still has the following advantages: (1) the laser power is optimally used because most of the laser light is still concentrated in the required length of the focal line and (2) a uniform spot size along the focal line-and thus a uniform separation of the parts from the substrate along the focal line-is obtained-which is brought about by the area of annular illumination and the required chromatic aberration set by other optical effects.

Unlike the plano-convex lens shown in fig. 4A, a focusing meniscus lens or another higher-order collimating focusing lens (aspherical, multi-lens system) may also be used.

In order to produce a very shortfocal line 2b using only the axicon andlens 11 combination shown in fig. 4A, it is necessary to select a very small beam diameter of the laser beam incident on the axicon. This has practical disadvantages: centering the beam onto the apex of the axicon must be very accurate and as a result is very sensitive to changes in the direction of the laser (beam drift stability). Furthermore, a strictly collimated laser beam is very diffuse, i.e. the beam cluster becomes blurred over short distances because of light deflection. By including a further lens (collimating lens 12) in theoptical assembly 6, both effects can be avoided. An additional positive (positive) collimatinglens 12 is used to very tightly adjust the circular illumination of the focusinglens 11. The focal length f' of thecollimator lens 12 is selected in the following manner: the desired circular diameter dr comes from the distance z1a of the monolith from thecollimator lens 12, which is equal to f'. The desired width br of the ring may be adjusted by the distance z1b (collimatinglens 12 to focusing lens 11). As a purely geometric temperature, a smaller width of the circular illumination results in a shorter focal line. A minimum value is obtained at the distance f'.

Thus, theoptical assembly 6 described in fig. 4A is based on the optical assembly shown in fig. 1, and therefore only the differences are described below. Thecollimator lens 12 is also designed here as a plano-convex lens (with its curvature facing the beam direction), which is additionally arranged centrally in the beam path between theaxicon 10 on one side (with its apex facing the beam direction) and the plano-convex lens 11 on the other side. The distance of thecollimator lens 12 from theaxicon 10 is referred to as z1a, the distance of the focusinglens 11 from thecollimator lens 12 is referred to as z1b, and the distance of thefocal line 2b from the focusinglens 11 is referred to as z2 (always viewed in the beam direction).

As is also shown in fig. 4A, the circular radiation SR formed by theaxicon 10 is incident divergently on thecollimator lens 12 and has a circular diameter dr, which can be adjusted along the distance z1b to the desired circular width br, so that an approximately constant circular diameter dr is formed at least at the focusinglens 11. In the case shown, it is expected that a very shortfocal line 2b is produced, reducing the circle width br of about 4mm at thelens 12 to about 0.5mm at thelens 11 because of the focusing properties of the lens 12 (in this embodiment, the circle diameter dr is 22 mm).

In the embodiment shown, a focal line length l of less than 0.5mm can be obtained using a typical laser beam diameter of 2mm, the focal length f of the focusinglens 11 being 25mm, the focal length f' of the collimating lens being 150mm, and the selected distance Z1a being Z1b being 140mm and Z2 being 15 mm.

It should be noted that the typical operation of such picosecond lasers forms "bursts" of pulses, sometimes referred to as "burst pulses". A burst is a laser operation in which the pulse emission is not a uniform and steady stream, but rather a tight cluster of pulses. This is shown in fig. 5. Each "pulse train" 610 can include a plurality of pulses 620 (e.g., at least 2 pulses, at least 3 pulses, at least 4 pulses, at least 5 pulses, at least 10 pulses, at least 15 pulses, at least 20 pulses, or more) having a very short duration. That is, the pulse bursts are pulse "packets," and the pulse bursts are separated from each other by a longer duration than between individual adjacent pulses within each pulse burst. Pulse duration T ofpulse 610_dCan be from about 0.1 picosecond to about 100 picoseconds (e.g., 0.1 picosecond, 5 picoseconds, 10 picoseconds, 15 picoseconds, 18 picoseconds, 20 picoseconds, 22 picoseconds, 25 picoseconds, 30 picoseconds, 50 picoseconds, 75 picoseconds, or the time therebetween). In some embodiments, the pulse duration may be greater than about 1 picosecond and less than about 100 picoseconds or greater than about 5 picoseconds and less than about 20 picoseconds. Single pulseTheseindividual pulses 620 within aburst 610 may also be referred to as "sub-pulses," which simply represents the fact that they occur within a single burst of pulses. The energy or intensity of eachlaser pulse 620 within aburst 610 may not be equal to the energy or intensity of other pulses within the burst, and the intensity distribution of multiple pulses within aburst 610 often follows an exponential decay over time, which is controlled by the laser design. In some embodiments, eachpulse 620 within apulse train 610 is separated in time by a duration T_pWhich is between about 1 nanosecond and about 50 nanoseconds, (e.g., 10-50 nanoseconds, or 10-30 nanoseconds), and the time is often controlled by the laser cavity design. The time interval T between each pulse within aburst 610 for a given laser_p(pulse-to-pulse interval) is relatively uniform (± 10%). For example, in some embodiments, T_pIs about 20 nanoseconds (50 MHz). Also for example, for generating a pulse to pulse interval T of about 20 nanoseconds_pThe laser of (2), pulse-to-pulse interval T within a pulse group_pTo stay within about + -10%, or about + -2 nanoseconds. The time between each "burst" 610 of pulses 620 (i.e., the time interval T between bursts)_b) Will be much larger, (e.g., 0.25 ≦ T_b≦ 1000 microseconds, e.g., 1-10 microseconds, or 3-8 microseconds). In some exemplary embodiments, T is the laser repetition frequency of about 100kHz_bIs about 10 microseconds. In some exemplary embodiments of the lasers described herein, T is the laser repetition rate or repetition frequency of about 200kHz_bMay be about 5 microseconds. For example, for a laser repetition rate of 200kHz, the time between each "burst" can also be about 5 microseconds. The laser repetition rate is also referred to herein as the burst repetition frequency and is defined as the time between the first pulse in a burst to the first pulse in a subsequent burst. In other embodiments, the burst repetition rate is from about 1kHz to about 4 MHz. More preferably, the laser repetition rate may be about 10kHz-650 kHz. In some embodiments, the laser repetition rate may be about 10kHz or greater, or about 100kHz or greater. The time T between the first pulse in each pulse group to the first pulse in the subsequent pulse group_bCan be 0.25 microseconds (4MHz repetition rate) -1000 microseconds (1kHz repetition)Rate), for example, 0.5 microseconds (2MHz repetition rate) -40 microseconds (25kHz repetition rate), or 2 microseconds (500kHz repetition rate) -20 microseconds (50kHz repetition rate). The exact timing, pulse duration and repetition rate may vary depending on the laser design, but shorter pulses (T) with high intensity have been shown to have_d<20 picoseconds, preferably T_dLess than or equal to 15 picoseconds) is particularly well effective. In someembodiments 5 picoseconds ≦ T_dLess than or equal to 15 picoseconds.

The energy required to change the material can be described by the burst energy-the energy contained within a burst (each burst 610 containing a series of pulses 620) or by the energy contained within a single laser pulse (many of which may contain a burst). For these applications, the energy/pulse train may be 25 microjoules-750 microjoules, more preferably 40 microjoules-750 microjoules, 50 microjoules-500 microjoules, 50-250 microjoules, or 100-. The energy of the individual pulses within a burst can be smaller, and the exact individual laser pulse energy will depend on the number of pulses within a burst and the decay rate (e.g., exponential decay) of the laser pulse over time, as shown in fig. 5. For example, for a constant energy/burst, if the burst contains 10 individual laser pulses, the energy of each individual laser pulse will be less than if the same burst contained only 2 individual laser pulses.

For such processing, it is preferable to use a laser that generates such a pulse train. The use of a pulse burst sequence that spreads the laser energy over a rapid sequence of sub-pulses (which make up the burst) allows for a high intensity interaction with the material over a longer time scale than can be formed using a single pulse laser, as opposed to using a single pulse separated in time by the laser repetition rate. Although a single pulse may be spread in time, in doing so the intensity within the pulse must drop by about the same factor as the pulse width increases. Thus, if the 10 picosecond pulse is extended to a 10 nanosecond pulse, the intensity will drop by about 3 orders of magnitude. This decrease may reduce the optical intensity to an extent where the nonlinear absorption is no longer significant and the optical-material interaction is no longer strong enough to effect material modification. In contrast, with a pulse burst pulsed laser, the intensity in each sub-pulse may still be very high-e.g., 3 10 picosecond pulses separated in time by about 10 nanoseconds still result in an intensity within each pulse that is within about 3 times that of a single 10 picosecond pulse, while now allowing the laser to interact with the material on a time scale that is three orders of magnitude higher than before. Thus, such modulation of the plurality of pulses within the pulse train enables manipulation of the time scale of the laser-material interaction in the following manner: the approach may facilitate more or less light interaction with the pre-existing plasma plume (plume), more or less light-material interaction and pre-excitation of atoms and molecules of the material by the initial or previous laser pulse.

When a single pulse burst of pulses impacts substantially the same location on the material, a damage track or hole is formed in the material. That is, multiple laser pulses within a single pulse burst correspond to a single defect line or hole location in the material. Of course, because the material is translated (e.g., by a constant motion stage) or the beam is moved relative to the material, the individual pulses within a pulse train cannot be precisely at the same spatial location on the material. However, a pulse must be within 1 micron of another pulse so that they impact the material at substantially the same location. For example, the pulses may impact the material at a separation sp from each other, where 0< sp ≦ 500 nanometers. For example, when a location on a material is impacted with a pulse train of 20 pulses, the individual pulses within the pulse train impact the glass within 250 nanometers of each other. Thus, in some embodiments, the spacing sp is from about 1nm to about 250nm or from about 1nm to about 100 nm.

The optical method of creating the line focus can take many forms, using a circular laser beam and a spherical lens, axicon lens, diffractive element, or other method to create a linear region of high intensity, as described above. The type (picosecond, femtosecond, etc.) and wavelength (IR, green, UV, etc.) of the laser may also be varied, provided that sufficient optical intensity is achieved to decompose the substrate material.

Hole or damage track formation:

the damage tracks formed by the laser methods described above are typically in the form of holes having an internal size of about 0.1 to 2 microns, for example 0.1 to 1.5 microns. Preferably, the size of the holes formed with the laser is very small (one micron or less) -i.e., they are narrow. In some embodiments, the pores have a diameter of 0.2 to 0.7 microns. As noted above, in some embodiments, the damage tracks are not continuous holes or channels. The damage tracks can have a diameter of 5 microns or less, 4 microns or less, 3 microns or less, 2 microns or less, or 1 micron or less. In some embodiments, the damage tracks can have a diameter of greater than 100nm to less than 2 microns, or greater than 100nm to less than 0.5 microns. Scanning electron micrographs of this feature are shown in fig. 6A and 6B. These holes are unetched holes (i.e., they have not been widened by the etching step).

The holes or defect lines/damage tracks may pass through the full thickness of the material and may be continuous openings throughout the depth of the material or not. FIG. 7 shows a through 150 micron thickness

Examples of such traces or lines of defects throughout the thickness of a glass substrate workpiece. The perforation or damage trace was observed through the side of the edge of the cleavage. The trace through the material is not necessarily a through hole. There are often areas of glass that plug the pores, but the glass size is usually small, e.g. on the order of micrometers.

Fig. 8 shows a larger magnification image of a similar hole or damage track, where the hole diameter can be seen more clearly, and there is also an area where the hole is blocked by the remaining glass. The diameter of the trace made through the glass was about 1 micron. The traces are not fully open-i.e., the area material is removed, but complete vias need not be formed.

Holes/damage tracks may also be punched or otherwise formed in the stack of stacked glass sheets or other substantially transparent materials. In this case, the focal line length needs to be longer than the stack height. For example, 150 microns using 3-fold stacking

Glass sheet is processedTests were conducted to prepare a full perforation through all 3 sheets, with perforations or defect lines/damage tracks (inside diameter about 1 micron) extending all the way from the top surface of the top sheet through the bottom surface of the bottom sheet. An example of configuring a focal line for full perforation through a single substrate is described with reference to fig. 2B-1, while full perforation through a 3-up stack of sheets is described below in connection with fig. 47. As defined herein, the internal diameter of a defect line or perforation is the internal diameter of an open channel or air hole. The diameter of the disturbed or altered regions of material surrounding the pores (e.g., densified, melted, or otherwise altered) can be greater than the internal diameter of the open channels or pores. The perforations in the stack may be acid etched to form a plurality of vias that extend through all of the glass sheets that make up the stack, or the glass sheets may be separated and the holes then acid etched in each of the sheets independently. For example, this method can result in a glass having etched holes with the following diameters: 1-100 microns, e.g., 10-75 microns, 10-50 microns, 2-25 microns, 2-20 microns, 2-15 microns, 2-10 microns, and the pores may have a spacing of, e.g., 25-1000 microns.

This process can also be used to form holes in a sheet of transparent material other than glass. Because the optical system uses line focusing, holes can be drilled through transparent materials with large (>1 micron, up to 4mm, e.g., 10-500 microns) air gaps or other filler materials (e.g., water, transparent polymers, transparent electrodes such as indium tin oxide) between substrate sheets. It should be noted that the ability to continuously drill through multiple glass sheets is a particular advantage of this linear focused drilling method, even when the glass sheets are separated macroscopically (many microns, tens of microns, or even hundreds of microns). In contrast, when other laser methods are used, such as those that rely on Kerr effect-based self-focusing to form high aspect ratio channels, or those that use glass holes themselves to form light guides, the presence of a gap, such as an air gap, between the two glass workpieces can completely upset the process, making high quality drilling of the bottom of the sheet difficult, or completely impossible. This is because when such a non-line-shaped focused (e.g., not a Gauss-Bessel) beam enters the air, it will diffract and spread out quickly. If there are no pre-existing channels to re-define the beam or no significant Kerr effect to refocus the beam, the beam will spread to too large a diameter to modify the underlying material. In the case of self-focusing based on the Kerr effect, the critical power for self-focusing in air is up to-20 times the critical power required in glass, which makes the air gap very problematic. However, for line focus systems, the beam continues to form a high intensity nucleus regardless of the presence of glass material or polymer, or air gaps, or even vacuum there. Thus, the line-shaped focused beam can continue to drill the lower glass layer regardless of whether there is a gap between the glass layer in the material and the upper glass sheet.

Similarly, the stack substrate sheet may comprise substrates having different glass compositions in all stacks. For example, one stack may comprise two substrate sheets of EagleXG glass and Corning (Corning) glass 2320. Alternatively, the stack of transparent substrate sheets may comprise a non-glass transparent inorganic material, such as sapphire. The substrate must be substantially transparent to the laser wavelength used to form the line focus, for example, the laser wavelength is 200nm to 2000nm, e.g., 1064nm,532nm,355nm, or 266 nm. In some embodiments, the substrate may also be transparent to at least one wavelength in the range of about 390nm to about 700 nm. In some embodiments, the substrate can transmit at least 70%, at least 75%, at least 80%, at least 85%, or at least 90% of at least one wavelength in the range of about 390nm to about 700 nm. Drilling/damage tracks in glass or other transparent materials can be used to form articles comprising a stack of substrates (either spaced apart or in direct contact with each other) having a plurality of holes formed through the stack, wherein the holes extend through each of the substrates, the holes having a diameter of, for example, 1-100 microns, and a spacing of, for example, 25-1000 microns. Thus, such a method can be used to form a substantially transparent article comprising a multilayer stack, wherein the multilayer stack comprises a plurality of glass layers and at least one polymer layer located between the glass layers, or at least two glass layers having different compositions, or at least one glass layer and at least one non-glass inorganic layer.

The lateral spacing (pitch) between holes or defect lines/damage tracks is determined by the pulse or pulse group frequency of the laser as the substrate is translated under the focused laser beam. Typically, only a single picosecond laser pulse train is required to form a complete hole, but multiple pulse trains can be used if desired. To form holes at different pitches, the laser may be fired to emit at longer or shorter intervals. In some embodiments, the laser excitation may be generally synchronized with stage-driven movement of the workpiece under the beam, so laser pulse bursts are excited at fixed intervals, such as every 1 micron, every 5 microns, every 10 microns, or every 20 microns or more. When damage tracks are formed in a substrate intended for use as an interposer, the distance or periodicity between adjacent damage tracks may depend on the desired via pattern (i.e., holes formed after the etching process). For example, in some embodiments, the desired damage track pattern (and the resulting vias formed therefrom after etching) is an irregularly spaced, non-periodic pattern. The damage track pattern needs to be at the location where the traces are placed on the intermediate layer or where the special electrical connections are to be made of the chip to be placed on the intermediate layer. Thus, the cutting and damage track drilling for the interposer is different in that the through holes of the interposer are arranged in a non-periodic pattern. However, for cutting patterns, the damage tracks are prepared with a particular periodic pitch, where the pitch depends on the composition of the material being cut. In the methods described herein, the spacing between adjacent holes/defect lines/damage tracks of a hole or defect line (damage track, or perforation) may be about 10 microns or greater, about 20 microns or greater, about 30 microns or greater, about 40 microns or greater, about 50 microns or greater. In some embodiments, the spacing may be up to about 20 mm. In some embodiments, the spacing may be from 50 microns to 500 microns or from 10 microns to 50 microns.

FIG. 9 shows a similar sample, in thiscase 300 micron thick corning from a top view

The glass has a periodic array of holes. The entry point of the laser beam is clearly seen. The pitch or spacing between adjacent holes is 300 microns and the approximate diameter of the holes is 2 micronsRice, and there is an edge or modified or raised material of about 4 microns diameter around each hole. Various laser processing parameters have been explored to find conditions that produce the following holes: the hole penetrates the material completely and has very little glass microcracking.

Laser power and lens focal length (which determines focal line length and hence power density) are particularly important parameters to ensure complete penetration through the glass and lower microcracking. For example, fig. 10 shows the results in which significant glass microcracking occurred.

It is also possible to deliberately form perforations or damage tracks which extend only partially through the material. In this case, such traces can be used to prepare blind vias or through vias (via). An example of a laser formed blind via is shown in fig. 11. Here, the damage tracks extend through about 75% of the glass. To achieve this, the focusing of the optics is increased until the line focus only causes damage in the top portion of the glass. Other blind hole depths may be implemented, such as extending only 10%, 25%, 50% or any fractional value of the glass thickness through the glass.

The following conditions were found to be suitable for healing at 300 microns thickness

Damage tracks are formed in the glass, which are continuous or discontinuous through holes or channels extending from the first surface to the second surface:

the input beam diameter to the axicon lens is about 3mm1/e²

Shaft-edge taper angle of 10 °

Initial collimator lens focal length of 125mm

Final objective focal length of 50mm

Angle of convergence of incident beam (beta) 12.75 deg

Focus was set at z 0.25mm (about 50 microns below the top surface of the part)

Laser pulse energy is about 180 microjoules)

The laser pulse repetition rate was 200 kHz.

3 pulses/pulse groups

The results of these conditions are shown in FIG. 9.

For cutting operations, the laser excitation is typically synchronized with the stage-driven movement of the part under the beam, and the laser pulses are most commonly excited at fixed intervals, for example every 1 micron or every 5 microns. The exact spacing is determined by the material properties that promote crack propagation from perforation to perforation at a given stress level in the substrate. However, instead of cutting the substrate, the same method can also be used to perforate only the material with a greater distance between holes or damage tracks. In the case of an interposer, the holes are typically spaced at a distance much greater than that required for cutting-not a pitch of about 10 microns or less, but the spacing between holes may be several hundred microns. As mentioned above, the exact location of the holes need not have regular spacing (i.e., they are non-periodic) -the location is determined only by the time the laser is fired and can be at any location within the part. The holes prepared in fig. 8 are examples of spacing and patterns for some representative interposer applications.

In general, the higher the laser power available, the faster perforations can be made in the material and/or the faster damage tracks can be made in the material using the above-described method. In the case of drilling glass for interleaf or similar applications, the processing speed is generally not directly limited by the laser power, but more by the ability to direct an already abundant laser pulse or burst to the specific location where the hole is required. As described above, in some embodiments, the desired damage track pattern (and the resulting vias formed therefrom after etching) is an irregularly spaced, non-periodic pattern. The damage track pattern needs to be at the location where the traces are placed on the intermediate layer or where the special electrical connections of the chip are to be made on the intermediate. Thus, the cutting and damage track drilling for the interposer is different in that the through holes of the interposer are arranged in a non-periodic pattern. For example, a commercially available burst mode picosecond laser can conveniently generate laser bursts of 200 microjoules per burst at a repetition rate of-100 and 200 kHz. This corresponds to a time-averaged laser power of about 20-40 watts. However, to drill an intervening layer, often most of these pulse bursts are not utilized because the beam can only be set at the desired hole location at a rate of kHz or perhaps tens of kHz, even with the very fast beam deflection method. This means that the main challenge for effective drilling using the line focus and picosecond pulsed laser methods described above is how to move and direct the beam across the substrate surface. One method may be used to segment the hole pattern into a series of one-dimensional lines, where each line contains all of the holes, e.g., holes sharing the same y-axis position. The glass or beam may then be scanned in a "raster scan" mode, in which the laser beam is moved in the x-direction, scanning across all desired aperture locations that share the same y-axis value. As the beam is scanned, the laser is fired to emit bursts only at the desired aperture locations. After scanning a given y-line, the substrate or laser beam is moved to a new y-position and the process is repeated for a new set of desired hole positions on the new y-line. This process is then continued until all of the desired pores on the substrate have been prepared.

The above process is simple but not necessarily efficient, as the speed of the stage and the required hole spacing will determine how many fractions of laser pulses/bursts can be used. For example, if the laser can generate pulses or bursts at a speed of 200,000 bursts/second, but the stage is moving at an average speed of 0.5 m/second and the holes are on average 100 microns apart, then only about 5,000 bursts/second-about 2.5% of the available laser bursts are used. While this did drill 5,000 holes (or damage tracks) per second, this was only a small fraction of the laser capacity.

A more efficient way of directing the laser beam can be used. Scanning of the glass or beam delivery optics may be combined with fast beam deflection, which may come from galvanometer mirrors (galvo) and f-theta lenses, or with piezo actuation of the optics or glass or small range, or electro-optic beam deflection (EOD) or acousto-optic beam deflection (AOD), to enable fast adjustment of the beam in a direction perpendicular to the linear "raster" scanning direction as described above. In this case, because the beam is scanned along the y-axis, small and fast adjustments can be made using a fast beam deflector, which allows pulses to be directed to any aperture within a certain range of the linear stage (x, y) coordinates in a given time. Thus, rather than directing the laser beam aperture only along a given position of the line, the system can now direct the laser beam to any aperture within the scratch (swipe) width dy of the raster scan line. This can greatly increase the number of holes per unit time that the laser beam can enter, and thus greatly increase the number of holes per second that can be drilled. Furthermore, fast beam deflectors can be used not only in the direction perpendicular to the raster scan axis, but also parallel to the scan axis. Furthermore, by flexing the beam parallel to the scan axis, a fast beam flexure assembly (e.g., galvanometer, AOD, EOD, piezo) may be used to achieve drilling of holes within dy's scribe having the same scan axis position (e.g., x-axis in the above embodiments) but having different y-axis positions, since the beam may "move" backwards relative to the stage scan without stopping the linear stage movement to drill a second hole at a given x-position. Furthermore, the rapid deflection along the scan axis also allows for more precise placement of the aperture, as it can be used to direct the beam to the desired x-axis position, regardless of any small time lag in the time that the pulsed laser can be used to fire the pulse bursts, and also compensates for velocity and acceleration artifacts (artifacts) in the linear stage movement.

Alternatively, rather than using continuous scanning in one direction and fast beam movement in coordination with the scanning, a more traditional "step and repeat" method can be used in which the linear stage is moved to a specific (x, y) position, all holes within some field of fast beam deflectors (e.g., galvanometers) are drilled, and the linear stage is stepped to a new (x, y) position and the process repeated. Then, for overall drilling speed, the above-described coordinated linear stage and fast deflector method can be preferably used, wherein the linear stage is kept almost constantly moving.

To achieve even higher system throughput (aperture/sec/system), the beam scanning methods described above can also be combined with beam splitting techniques, where a common laser source distributes its pulse bursts among multiple beam delivery heads on a single substrate or a sequence of substrates. For example, acousto-optic or electro-optic elements may be used to deflect every nth pulse to a given optical path, and N optical heads may be used. This can be achieved by: the angular deflection properties of such beam steering elements, or the polarization-varying properties of such elements, are used to direct the beam through a polarization-dependent beam splitter.

Depending on the desired pattern damage tracks (and vias formed therefrom by the etching process), the damage tracks can be formed at the following rates: greater than about 50 damage tracks/second, greater than about 100 damage tracks/second, greater than about 500 damage tracks/second, greater than about 1,000 damage tracks/second, greater than about 2,000 damage tracks/second, greater than about 3,000 damage tracks/second, greater than about 4,000 damage tracks/second, greater than about 5,000 damage tracks/second, greater than about 6,000 damage tracks/second, greater than about 7,000 damage tracks/second, greater than about 8,000 damage tracks/second, greater than about 9,000 damage tracks/second, greater than about 10,000 damage tracks/second, greater than about 25,000 damage tracks/second, greater than about 50,000 damage tracks/second, greater than about 75,000 damage tracks/second, or greater than about 100,000 damage tracks/second.

Etching:

to enlarge the hole to a size that can be used for metal/conductive material coating/filling and electrical connection, the part is acid etched. The use of acid etching to enlarge the pores to a final diameter can have several benefits 1) acid etching changes the pores from a size too small to be metallized and for the intervening layer (e.g., about 1 micron) to a more convenient size (e.g., 5 microns or higher); 2) etching may begin with a discontinuous hole or simply a damage track through the glass and etch it away to form a continuous via; 3) etching is a highly parallel process in which all holes/damage tracks in a part are simultaneously enlarged-much faster than if the laser had to contact the hole again and drill away more material to enlarge the hole; and 4) etching helps to passivate any edges or small cracks within the part, which increases the overall strength and reliability of the material.

Fig. 51A and 51B show thesubstrate 1000 after laser drilling and after acid etching, respectively. As shown in fig. 51A, thesubstrate 1000 may be subjected to any of the laser drilling methods described above to form one or more damage tracks or guideholes 1002 extending from a first ortop surface 1004 to a second orbottom surface 1006. The damage tracks 1002 are shown as continuous holes for illustrative purposes only. As described above, in some embodiments, thedamage tracks 1002 are non-continuous pores, wherein substrate particles are present in the damage tracks. As shown in fig. 51B, after subjecting thesubstrate 1000 to any of the etching processes described below, the damage tracks are enlarged to form via holes 1008 having a top diameter Dt at the top opening of thetop surface 1004, a bottom diameter Db at the bottom opening of thebottom surface 1006, and a waist diameter Dw. As used herein, the waist refers to the narrowest portion of the aperture located between the top and bottom openings. While the contour of the through-hole 1008 is shown as being hourglass-shaped due to the waist, this is merely exemplary. In some embodiments, the through-hole is substantially cylindrical. In some embodiments, the etching process produces a via having a diameter of: greater than 1 micron, greater than about 2 microns, greater than about 3 microns, greater than about 4 microns, greater than about 5 microns, greater than about 10 microns, greater than about 15 microns, or greater than about 20 microns.

In one embodiment, the acid used is 10% HF/15% HNO by volume₃. The part was etched at a temperature of 24-25 c for 53 minutes to remove approximately 100 microns of material. The part was immersed in this acid bath and ultrasonically agitated using a combination of 40kHz and 80kHz frequencies to promote fluid penetration and fluid exchange in the hole/damage tracks. In addition, manual agitation (e.g., mechanical agitation) of the part is performed within the ultrasonic field to prevent standing wave patterns from the ultrasonic field from forming "hot spots" or cavitation-related damage on the part, and to provide macroscopic fluid flow across the part. The acid composition and etch rate were deliberately designed to slowly etch the part-material removal rate of only 1.9 microns/minute. An etch rate of less than, for example, about 2 microns/minute allows the acid to completely penetrate the narrow pores/damage tracks and stir to exchange fresh fluid and remove dissolved material from the very narrow pores/damage tracks from the start. This allows the holes to expand at nearly the same rate throughout the thickness of the substrate (i.e., the entire length of the hole or damage track) during the etching process. In some embodiments, the etch rate may be a rate of less than about 10 microns/minute, such as a rate of less than about 5 microns/minute, or a rate of less than about 2 microns/minute.

Fig. 12A and 12B show top and bottom views of the resulting part. The diameter of the pores was about 95 microns and very round, indicating that there was very little microcracking of the material. The pitch of the holes is 300 microns and the diameter of each hole is about 90-95 microns. The images in fig. 12A and 12B were obtained using a backlight, and the bright areas within each hole also indicate that the hole has been completely opened by acid etching. The same sample was cut into small pieces to more closely view the internal profile of the hole. Fig. 14 and 15 show the results. The holes have an "hourglass" shape, i.e. they taper towards the middle of the hole. Typically, this shape is determined by the etching environment, not by the pilot hole formation process. The bright areas are glass and the dark areas are holes. The top (laser incident) diameter of the hole is about 89 microns in diameter, the waist is about 71 microns, and the bottom (laser exit) diameter is about 85 microns.

In contrast, fig. 13 shows the results of etching a sample with significant microcracking from laser machining-the holes are etched into elongated shapes rather than circular features. Microcracking can be reduced by: decreasing the laser burst energy, increasing the number of pulses/burst, or increasing the length of the line focus, for example using a longer focal length objective lens. These variations can reduce the energy density contained within the substrate. In addition, care must be taken to ensure optimal alignment of the optical system so that chromatic aberration is not introduced into the line focus, which creates azimuthal asymmetry in the line focus. This asymmetry can introduce high energy density sites within the substrate that can lead to microcracking.

To confirm that this laser and etching process gave consistent results, a 100x100 array (10,000 total hole count) of hole patterns with a pitch of 300 microns was prepared and the etched samples were then measured using a mechanical imaging system to obtain the top and bottom diameters and waist diameter of each hole. The results are shown as histograms in FIGS. 16A-16C. The top and bottom diameters were both about 95 microns in diameter, the dimensions were very close, and the standard deviation was about 2.5 microns. Unlike the top and bottom diameters, the waist is about 70 microns with a standard deviation of about 3 microns. Thus, the waist is about 30% narrower than the top and bottom diameters. 17A-17C show histograms of roundness measurements of the top, bottom, and waist of the same wells. Roundness is defined as the maximum diameter of a hole minus the minimum diameter of the same hole and is given in microns. The distribution indicates that the pores are substantially circular to less than about 5 microns. There is no significant tail in the profile that would otherwise indicate micro-cracks or gaps etched to a non-circular shape.

After forming the acid etched substrate shown in fig. 12A-15 and having the features shown in fig. 16A-17C, it was found that the acid etching conditions can be varied to adjust the various features of the vias so that they can be used as through vias for the interposer. In some embodiments, for example, a via may have a top opening, a bottom opening, and a waist, and the ratio of the waist diameter to the top or bottom opening diameter may be controlled. As used herein, the waist refers to the narrowest portion of the aperture located between the top and bottom openings. Two factors controlling the waist diameter, top opening, and bottom opening are the etch reaction rate and diffusion rate. In order to etch away the entire thickness of the substrate to enlarge the damage tracks into through vias, the acid needs to traverse the entire length of the damage tracks. If the etch rate is too fast so that the acid does not have enough time to diffuse and reach all parts of the damage track, the acid will disproportionately etch more material away at the surface of the material than in the middle of the material. The Theiler modulus of the etching process can be controlled

Such as thele E.W (Thiele, E.W.) "relationship between catalytic activity and particle size", "industrial and engineering chemistry", 31(1939), page number: 916, 920 to control the ratio of the waist diameter to the diameter of the top or bottom opening. The thele modulus is the ratio of diffusion time to etch reaction time and is expressed by the following equation:

wherein:

k_ris the reaction rate constant of the etch;

c is the bulk acid concentration;

γ is a factor based on the number of kinetic reaction steps;

r is the radius of the pores during the reaction;

D_{is effective}Is the effective diffusion coefficient of acid through water into the damage tracks or pores, which is the natural diffusion coefficient D of amplification enhanced by stirring and ultrasound; and

l is 1/2 of material thickness.

According to the above formula, the theiler modulus is greater than 1 when the etch reaction time is greater than the diffusion time. This means that the acid is depleted before it passes the entire length of the damage track or hole and can be replenished by diffusion in the center of the damage track or hole. As a result, etching proceeds faster at the top and bottom of the trace or hole and from k_rControlled, the etching in the center will proceed more slowly and the rate is controlled by diffusion, which results in an hourglass-like shape of the via. However, if the diffusion time is equal to or greater than the etch reaction time, the theiler modulus is less than or equal to 1. Under such conditions, the acid concentration along the entire damage tracks or holes is uniform and the damage tracks or holes will be uniformly etched to form substantially cylindrical through-holes.

In some embodiments, the diffusion time and etch reaction time can be controlled to control the theler modulus of the etching system and thereby control the ratio of the waist diameter to the top and bottom opening diameters. FIG. 52 shows the relationship between the Therler (Thiele) modulus of the etching system and the expected waist diameter in percent relative to the top and bottom opening diameters. In some embodiments, the theler modulus of the etching process may be less than or equal to about 5, less than or equal to about 4.5, less than or equal to about 4, less than or equal to about 3.5, less than or equal to about 3, less than or equal to about 2.5, less than or equal to about 2, less than or equal to about 1.5, or less than or equal to about 1. In some embodiments, the waist diameter of a through-hole is 50% -100%, 50% -95%, 50% -90%, 50% -85%, 50% -80%, 50% -75%, 50% -70%, 55% -100%, 55% -95%, 55% -90%, 55% -85%, 55% -80%, 55% -75%, 55% -70%, 60% -100%, 60% -95%, 60% -60%, 60% -85%, 60% -80%, 60% -75%, 60% -70%, 65% -100%, 65% -95%, 65% -90%, 65% -85%, 65% -80%, 65% -75%, 65% -70%, 70% -100%, 70% -95%, 70% -90%, 70% -85%, 70% -80%, 70% -75%, 75% -100%, 75% -95%, 75% -90%, 75% -85%, 75% -80%, 80% -100%, 80% -95%, 80% -90%, 80% -85%, 85% -100%, 85% -95%, 85% -90%, 90% -100%, 90% -95%, or 95% -100%. In some embodiments, the diameter of the waist of the through-hole is about 50% or greater, about 55% or greater, about 60% or greater, about 65% or greater, about 70% or greater, about 75% or greater, about 80% or greater, about 85% or greater, about 90% or greater, about 95% or greater, or about 100% of the diameter of the top opening and/or the diameter of the bottom opening of the through-hole. In some embodiments, the waist diameter of the through-hole is 50% -100%, 50% -95%, 50% -90%, 50% -85%, 50% -80%, 50% -75%, 50% -70%, 55% -100%, 55% -95%, 55% -90%, 55% -85%, 55% -80%, 55% -75%, 55% -70%, 60% -100%, 60% -95%, 60% -60%, 60% -85%, 60% -80%, 60% -75%, 60% -70%, 65% -100%, 65% -95%, 65% -90%, 65% -85%, 65% -80%, 65% -75%, 65% -70%, 70% -100%, 70% -95%, 70% -90%, 70% -85%, 70% -80%, 70% -75%, 75% -100%, 75% -95%, 75% -90%, 75% -85%, 75% -80%, 80% -100%, 80% -95%, 80% -90%, 80% -85%, 85% -100%, 85% -95%, 85% -90%, 90% -100%, 90% -95%, or 95% -100%. In some embodiments, the diameter of the waist of the through-hole is about 50% or greater, about 55% or greater, about 60% or greater, about 65% or greater, about 70% or greater, about 75% or greater, about 80% or greater, about 85% or greater, about 90% or greater, about 95% or greater, or about 100% of the average of the top opening diameter and the bottom opening diameter of the through-hole.

As can be determined from the above-mentioned theiler's modulus equation, the initial radius of the damage track and the glass thickness contribute to the theiler's modulus. Fig. 53 shows how the theler modulus decreases with the initial radius of the damage track. Fig. 54 shows how the theler modulus increases with half the thickness of the substrate. In some cases, the substrate thickness and damage track radius are factors that cannot be changed if a certain thickness or damage track radius is desired. Therefore, in this caseNext, other factors that affect the theler modulus may be adjusted. For example, FIG. 55 shows how the Theiler modulus follows the effective diffusion coefficient (D)_{Is effective}) Is increased and decreased. In some embodiments, the effective diffusion coefficient may be increased by adding agitation and/or sonication to the etching conditions, as described in more detail below. FIG. 56 shows how the Tiler modulus decreases with decreasing acid concentration, in this example HF concentration. Figure 56 also shows how the combination of increasing the effective diffusion coefficient and decreasing the acid concentration decreases the theler modulus.

In some embodiments, the etch reaction time may be controlled by adjusting the acid concentration in the etching solution. In some embodiments, the etching solution may be an aqueous solution comprising deionized water, a primary acid, and a secondary acid. The primary acid may be hydrofluoric acid and the secondary acid may be nitric acid, hydrochloric acid or sulfuric acid. In some embodiments, the etching solution may comprise only the primary acid. In some embodiments, the etching solution may comprise a primary acid other than hydrofluoric acid and/or a secondary acid other than nitric, hydrochloric, or sulfuric acid. Exemplary etching solutions may comprise 10 volume% hydrofluoric acid/15 volume% nitric acid or 5 volume% hydrofluoric acid/7.5 volume% nitric acid, or 2.5 volume% hydrofluoric acid/3.75 volume% nitric acid.

In some embodiments, orientation of the substrate in the etch bath, mechanical agitation, and/or addition of surfactants to the etching solution are other etching conditions that may be modified to adjust the through-hole features. In some embodiments, the etching solution is ultrasonically agitated, and the substrate is oriented in an etch bath containing the etching solution such that the top and bottom openings of the damage tracks receive substantially uniform exposure to the ultrasonic waves, thereby uniformly etching the damage tracks. For example, if the ultrasonic sensor is placed at the bottom of the etch bath, the substrate may be oriented in the etch bath such that the surface of the substrate with the damage tracks is perpendicular to the bottom of the etch bath rather than parallel to the bottom of the etch bath.

In some embodiments, the etch bath may be mechanically agitated in the x, y, and z directions to improve uniform etching of damage tracks. In some embodiments, the mechanical agitation in the x, y, and z directions may be continuous.

In some embodiments, a surfactant may be added to the etching solution to increase the wetting ability of the damage tracks. Increased wetting ability reduces diffusion time and may allow for an increase in the ratio of the through-hole waist diameter to the through-hole top and bottom opening diameters. In some embodiments, the surfactant can be any suitable surfactant that dissolves in the etching solution and does not react with the acid in the etching solution. In some embodiments, the surfactant may be a fluorosurfactant such as

FS-50 orFS-54. In some embodiments, the concentration of surfactant, expressed in milliliters of surfactant per liter of etching solution, may be about 1, about 1.1, about 1.2, about 1.3, about 1.4, about 1.5, about 1.6, about 1.7, about 1.8, about 1.9, about 2, or greater.

Speed:

one of the main advantages of using the method described above for making perforations or "pilot holes" or "damage tracks" by means of laser light is the extremely fast processing times. Each of the damage tracks shown in fig. 7 was prepared using a single burst of picosecond laser pulses. This is in essence different from percussion drilling, which requires many laser pulses to gradually remove a layer of material.

For the samples shown here, the platform speed was 12 m/min-200 mm/sec. For a 300 micron interval, this means that a burst of laser pulses is fired every 1.5 milliseconds to form a hole, with a formation rate of 667 holes/second. The stage acceleration and deceleration was calculated to produce each row of this approximately 30mmx30mm hole pattern with a hole formation rate well in excess of 300 holes/second. If the physical range of pattern preparation is larger, the frequency of plateau acceleration is lower and the average pore formation rate will be faster.

Since the laser used here can easily provide 100,000 pulses/second at full pulse energy, holes can be formed at this rate. Generally, the limit on the rate of hole formation is how fast the laser beam can be moved relative to the substrate. If the holes are 10 microns apart and the platen velocity is 1 m/sec, then 100,000 holes/sec are formed. In fact, it is often done to cut the substrate. But for actual interleaf layers, the holes are often hundreds of microns apart and the spacing is more random (i.e. there is a non-periodic pattern). Thus, the number of holes/second for the pattern shown is only about 300 holes/second as described above. To obtain higher velocities, the stage speed can be increased, for example from 200 mm/sec to 1 m/sec, which achieves a further 5-fold increase in speed. Similarly, if the average pore pitch is less than 300 microns, the rate of pore formation will increase by the same amount.

In addition to translating the substrate under the laser beam, other methods can be used to rapidly move the laser from hole to hole: the optical head itself is moved, using a galvanometer and an f-theta lens, an acousto-optic deflector, a spatial light modulator, and the like.

As mentioned above, depending on the desired pattern damage tracks (and vias formed therefrom by the etching process), the damage tracks can be formed at the following rates: greater than about 50 damage tracks/second, greater than about 100 damage tracks/second, greater than about 500 damage tracks/second, greater than about 1,000 damage tracks/second, greater than about 2,000 damage tracks/second, greater than about 3,000 damage tracks/second, greater than about 4,000 damage tracks/second, greater than about 5,000 damage tracks/second, greater than about 6,000 damage tracks/second, greater than about 7,000 damage tracks/second, greater than about 8,000 damage tracks/second, greater than about 9,000 damage tracks/second, greater than about 10,000 damage tracks/second, greater than about 25,000 damage tracks/second, greater than about 50,000 damage tracks/second, greater than about 75,000 damage tracks/second, or greater than about 100,000 damage tracks/second.

Final part:

in some embodiments, subjecting the substrate to the damage track formation and acid etching processes described above can result in a substrate having a plurality of through holes. In some embodiments, the diameter of the through-holes can be about 30 microns or less, about 25 microns or less, about 20 microns or less, about 15 microns or less, about 10 microns or less, about 5 to about 10 microns, about 5 to about 15 microns, about 5 to about 20 microns, about 5 to about 25 microns, about 5 to about 30 microns, or up to several tens of microns, depending on the requirements of the intended application. In other embodiments, the diameter of the through-hole may be greater than about 20 microns. In some embodiments, the substrate can haveThere are vias having different diameters, for example the vias may have a difference in diameter of at least 5 microns. In some embodiments, the difference in the top and bottom opening diameters of the via may be 3 microns or less, 2.5 microns or less, 2 microns or less, 1.5 microns or less, or 1 micron or less, which may be achieved by using a line-shaped focused beam to form damage tracks in the material. These damage tracks remain of very small diameter throughout the depth of the substrate, which ultimately results in uniform top and bottom diameters after etching. In some embodiments, the spacing (center-to-center distance) between adjacent vias can be about 10 microns or greater, about 20 microns or greater, about 30 microns or greater, about 40 microns or greater, about 50 microns or greater. In some embodiments, the spacing of adjacent through holes may be up to about 20 mm. In some embodiments, the via density can be about 0.01 vias/mm²Or greater, about 0.1 through holes/mm²Or greater, about 1 via/mm²Or greater, about 5 through holes/mm²Or greater, about 10 through holes/mm²Or greater, about 20 through holes/mm²Or greater, about 30 through holes/mm²Or greater, about 40 through holes/mm²Or greater, about 50 through holes/mm²Or greater, about 75 through holes/mm²Or greater, about 100 through holes/mm²Or greater, about 150 through holes/mm²Or greater, about 200 through holes/mm²Or greater, about 250 through holes/mm²Or greater, about 300 through holes/mm²Or greater, about 350 through holes/mm²Or greater, about 400 through holes/mm²Or greater, about 450 through holes/mm²Or greater, about 500 through holes/mm²Or greater, about 550 through holes/mm²Or greater, about 600 through holes/mm²Or greater, or about 650 through holes/mm²Or larger. In some embodiments, the via density can be about 0.01 vias/mm²About 650 through holes/mm²Or about 5 through holes/mm²About 50 through holes/mm²。

As noted above, in some embodiments, the waist diameter of a through-hole is 50% -100%, 50% -95%, 50% -90%, 50% -85%, 50% -80%, 50% -75%, 50% -70%, 55% -100%, 55% -95%, 55% -90%, 55% -85%, 55% -80%, 55% -75%, 55% -70%, 60% -100%, 60% -95%, 60% -60%, 60% -85%, 60% -80%, 60% -75%, 60% -70%, 65% -100%, 65% -95%, 65% -90%, 65% -85%, 65% -80%, 65% -75%, 65% -70%, 70% -100%, 70% -95%, 70% -90%, 70% -85%, 70% -80%, 70% -75%, 75% -100%, 75% -95%, 75% -90%, 75% -85%, 75% -80%, 80% -100%, 80% -95%, 80% -90%, 80% -85%, 85% -100%, 85% -95%, 85% -90%, 90% -100%, 90% -95%, or 95% -100%. In some embodiments, the diameter of the waist of the through-hole is about 50% or greater, about 55% or greater, about 60% or greater, about 65% or greater, about 70% or greater, about 75% or greater, about 80% or greater, about 85% or greater, about 90% or greater, about 95% or greater, or about 100% of the diameter of the top opening and/or the diameter of the bottom opening of the through-hole. In some embodiments, the waist diameter of the through-hole is 50% -100%, 50% -95%, 50% -90%, 50% -85%, 50% -80%, 50% -75%, 50% -70%, 55% -100%, 55% -95%, 55% -90%, 55% -85%, 55% -80%, 55% -75%, 55% -70%, 60% -100%, 60% -95%, 60% -60%, 60% -85%, 60% -80%, 60% -75%, 60% -70%, 65% -100%, 65% -95%, 65% -90%, 65% -85%, 65% -80%, 65% -75%, 65% -70%, 70% -100%, 70% -95%, 70% -90%, 70% -85%, 70% -80%, 70% -75%, 75% -100%, 75% -95%, 75% -90%, 75% -85%, 75% -80%, 80% -100%, 80% -95%, 80% -90%, 80% -85%, 85% -100%, 85% -95%, 85% -90%, 90% -100%, 90% -95%, or 95% -100%. In some embodiments, the diameter of the waist of the through-hole is about 50% or greater, about 55% or greater, about 60% or greater, about 65% or greater, about 70% or greater, about 75% or greater, about 80% or greater, about 85% or greater, about 90% or greater, about 95% or greater, or about 100% of the average diameter of the top and bottom openings of the through-hole.

In some embodiments, the aspect ratio (substrate thickness: via diameter) of the through-holes may be about 1:1 or greater, about 2:1 or greater, about 3:1 or greater, about 4:1 or greater, about 5:1 or greater, about 6:1 or greater, about 7:1 or greater, about 8:1 or greater, about 9:1 or greater, about 10:1 or greater, about 11:1 or greater, about 12:1 or greater, about 13:1 or greater, about 14:1 or greater, about 15:1 or greater, about 16:1 or greater, about 17:1 or greater, about 18:1 or greater, about 19:1 or greater, about 20:1 or greater, about 25:1 or greater, about 30:1 or greater, or about 35:1 or greater. In some embodiments, the aspect ratio of the through-holes may be from about 5:1 to about 10:1, from about 5:1 to 20:1, from about 5:1 to 30:1, or from about 10:1 to 20:1 from about 10:1 to 30: 1.

In some embodiments, the substrate has a thickness of about 20 microns to about 3mm, about 20 microns to about 1mm, or about 50 microns to 300 microns, or 100 microns to 750 microns, or about 1mm to about 3 mm. In some embodiments, the substrate may be made of a transparent material, including, but not limited to, glass, fused quartz, synthetic quartz, glass-ceramics, and crystalline materials such as sapphire. In some embodiments, the substrate can be glass, and the glass can comprise an alkali-containing glass, an alkali-free glass (e.g., an alkali-free alkali boroaluminosilicate glass), or a laminated glass piece, and the layers comprise different glass compositions. In some embodiments, the glass can be a chemically strengthened (e.g., ion exchanged) glass. In some embodiments, the substrate may be transparent to at least one wavelength in the range of about 390nm to about 700 nm. In some embodiments, the substrate can transmit at least 70%, at least 75%, at least 80%, at least 85%, or at least 90% of at least one wavelength in the range of about 390nm to about 700 nm.

The vias may then be coated and/or filled with a conductive material and used for electrical interposer applications. In some embodiments, the coating and/or filling may be performed by metallization. For example, metallization may be performed by vacuum deposition, electroless plating, filling with a conductive paste, or various other methods. After that, electrical traces can be patterned on the surface of the part, and a series of redistribution layers and contact pads can be formed, which enable routing of electrical signals from the holes to connections on the microchip or other circuitry.

For biochemical applications, such as digital polymerase chain reaction (dPCR), parts can also be functionalized with coatings that achieve control of the hydrophilic or hydrophobic properties of the surface. Other coatings may also be applied which enable the attachment of antibodies, proteins or other biomolecules. For dPCR microarrays, substrates with very dense and regular arrays of pores are particularly useful — for example, patterns of hexagonal close-packed pores with pitches less than about 100 microns. For such patterns, the speed of formation possible using the above laser method is particularly high, since the laser can be emitted extremely frequently and the full repetition rate of the laser is used efficiently. Thus, pore formation rates in excess of 10,000 pores/second (1 m/second plateau velocity and 100 micron pore spacing) can be achieved. It should be noted that hole formation may utilize only a small fraction of the laser pulse. The laser burst repetition rate can easily be several hundred kHz, but it is difficult to direct the beam to a new aperture location at a rate large enough to use all of these bursts. For example, the actual pore formation rate may be 100 pores/sec, 500 pores/sec, 999 pores/sec, 3,000 pores/sec, 5,000 pores/sec, 10,000 pores/sec, while the laser repetition rate may be 100,000 bursts/sec, 200,000 bursts/sec at the same time. In these cases, the majority of the pulse burst pulses are redirected by a device such as an electro-optic modulator into a beam dump (beam dump), rather than out of the laser and to the substrate. Thus, a smaller number of bursts/sec is used for drilling than is available from virtually the full repetition rate of the laser. Many short-pulse lasers have an electro-optical or acousto-optical modulator at their output so that they operate in this manner.

Examples

Example 1

Preparation of kangning

Glass (300 micron thickness) test samples were used to prepare through holes in the samples, see fig. 18B and 18C. Minor radial cracks in the glass in the range of about 10 microns were observed in all samples, as shown in fig. 18A, despite varying the burst energy and number of pulses per picosecond of the laser pulse burst, and varying the pitch from 50 microns to 300 microns.

Preparation of kangning

An additional sample of glass (150 micron thickness) was used to prepare the via hole, which was then enlarged by etching to the diameter of the hole. The parts are as follows: 100x100 hole array with a pitch of 300 microns, varying laser power or burst energy (5 samples), one sample with 150x150 hole array with a pitch of 200 microns, and one sample with 300x300 hole array with a pitch of 100 microns. As shown by the photo-optic before etching in fig. 19A-19C, top view (fig. 19A), bottom view (fig. 19B) and side view (fig. 19C), through holes were successfully prepared without significant nicks or cracks at the glass surface, but with some internal radial cracks and subsurface damage (not shown). As shown in fig. 20A-20E, a top view of a 100x100 array of holes with a pitch of 300 microns after (etching to about 100 micron diameter) etching with increased laser power (55% in fig. 20A, 65% in fig. 20B, 75% in fig. 20C, 85% in fig. 20D, and 100% in fig. 20E) indicates: the best results were obtained at higher power levels (most round holes, no blockage (dark center indicates blocked holes)), and best at about 75-85% power, the same results were also obtained from a bottom view of the same sample, shown in fig. 21A-21E (fig. 21A-55%, fig. 21B-65%, fig. 21C-75%, fig. 21D-85%, fig. 21E-100% laser power).

As shown in fig. 22A-22C, the larger array test results at 65% laser power (fig. 22A-150 x150 array, 200 micron pitch, 100 micron holes) (fig. 22B-22C-300 x300 array, 100 micron pitch, 50 micron holes) produced round holes for both 100 micron and 50 micron holes, but there was also some plugging, with some periodicity (likely due to ultrasonic standing waves forming smaller regions of higher or lower mixing during etching), and some regions with cracked and defective holes, as shown in fig. 22C.

Dimensional analysis on two 100x100 array samples showed that circularity (circularity-maximum inscribed diameter-minimum inscribed diameter) was good (i.e., less than about 5 microns), as shown in fig. 24A-24C for the first sample (fig. 24A-top, fig. 24B-bottom, fig. 24C-waist), and fig. 26A-26C for the second sample (fig. 26A-top, fig. 26B-bottom, fig. 26C-waist), and the top (first sample shown in fig. 23A, second sample shown in fig. 25A) and bottom (first sample shown in fig. 23B and second sample shown in fig. 25B) diameters were nearly equal, and the waist (first sample shown in fig. 23C and second sample shown in fig. 25C) was open.

Example 2

Tests for kangning

Additional samples of glass (300 micron thickness) were examined to examine how the pore quality varied with the final diameter (after etching). Vias were prepared in a 150x150 array (22,500 holes per sample) with a pitch of 300 microns using increasing laser power (55,65,75,85, and 100% laser power), and removal by etching yielded 4 hole diameters (30,50,75, and 100 micron diameter). The laser conditions for the via fabrication process were 50mm lens, 12 m/min (200 mm/sec) stage speed,200kHz repetition rate 3 pulses/burst. Vias were prepared at a rate of about 187 holes/sec. As shown in fig. 27A-27C for 30 micron wells and fig. 28A-28C for 50 micron wells, at 100% laser power, the waist over 30 micron wells appears narrowed (fig. 27B), while the waist over 50 micron wells (fig. 28B) is completely open. As shown in fig. 29A-29C for 75 micron pores and fig. 30A-30C for 100 micron pores, the waists (fig. 29B and 30B) are completely open in both dimensions at 100% laser power. As shown in fig. 31A-31C for 30 micron pores and fig. 32A-32C for 50 micron pores, at 85% laser power the waist on 30 micron pores appears narrowed (fig. 31B), while the waist on 50 micron pores (fig. 32B) is very open. As shown in fig. 33A-33C for 75 micron pores and fig. 34A-34C for 100 micron pores, the waists (fig. 33B and 34B) are completely open in both dimensions at 85% laser power. As shown in fig. 35A-35C for 30 micron wells and fig. 36A-36C for 50 micron wells, at 75% laser power, the waist over 30 micron wells appears narrowed (fig. 35B), while the waist over 50 micron wells (fig. 36B) is completely open. As shown in FIGS. 37A-37C for 75 micron holes and FIGS. 38A-38C for 100 micron holes, at 75% laser power, the waists in both dimensions (FIGS. 37B and 38B) are completely open, but overallThere may be some variation in pore size. As shown in fig. 39A-39C for 30 micron holes and fig. 40A-40C for 50 micron holes, at 65% laser power, no holes were completely formed inside the glass after etching, with the worst results on 30 micron holes (fig. 40B), although even 50 micron holes (fig. 40A) appeared somewhat lacking in openings or clogging. As shown in fig. 41A-41C for 75 micron holes and fig. 42A-42C for 100 micron holes, there was evidence of poor opening and clogging from top (fig. 41A and 42A) and bottom (fig. 41C and 42C) views at 65% laser power. As shown in fig. 43A-43C for 30 micron pores and fig. 44A-44C for 50 micron pores, at 55% laser power, the pores were not completely formed and the acid etch did not open them. As shown in fig. 45A-43C for 75 micron pores and fig. 46A-44C for 100 micron pores, at 55% laser power, the pores were not completely formed and the acid etch did not open them. As shown in fig. 46A and 46C in top and bottom views, respectively, even 100 micron pores show evidence of a lack of open waists or clogging.

Example 3

The methods described herein also achieve even higher processing speeds by allowing multiple layers to be drilled simultaneously. FIG. 47 shows 150 microns extending through a 3-up stack

A focal line 432 of the glass sheet 430. Because the focal line 432 extends through all 3 stacked sheets, a full perforation or a full line of defects may be formed through all 3 layers simultaneously. To form a complete perforation through the stack, the focal line length needs to be longer than the stack height. Once the parts are drilled, they can be separated and subsequently etched, which makes it easier for the acid to enter the pores of each piece.

A significant advantage of this line focusing method for drilling is that the method is not sensitive to air gaps between parts, unlike processes that rely on laser beam auto-focusing. For example, a focused Gaussian beam will diverge upon entering the first glass layer and not drill to a greater depth, or if self-focusing or waveguiding occurs due to reflections along the sides of the hole as the glass is drilled, the beam will exit the first glass layer and diffract and not drill into the second glass layer. Even in the case of a machining process that uses Kerr effect based self-focusing (sometimes referred to as "laser filamentation") to achieve a long interaction length within the material, it is a problem to have the laser beam exit the upper glass workpiece and enter the air, since it requires-20 times more power in the air to induce Kerr effect based self-focusing than it would require to maintain Kerr effect based self-focusing in the glass. In contrast, the Bessel beam will drill the glass layer over the full range of the line focus, regardless of the dimensional variations of the air gap (up to several hundred microns or even 1 mm).

Example 4

During such drilling, protective layers or coatings can also be inserted above, below and between the glass sheets. As long as the material is transparent to the laser radiation, the beam can still be focused through the protective coating and drill the glass workpiece. This may be particularly preferred if it is sought to keep the part clean and prevent scratching or other damage during drilling. After drilling the part, the coating may be removed. Similarly, a thin layer of such a layer, such as a transparent polymer (YY-100, a polyethylene self-adhesive film available from hong yuan Industrial co. ltd., dongguan), may be used between the sheets during stack drilling to prevent surface rubbing of one sheet on the other, which helps maintain part strength and prevent cosmetic or other defects.

FIG. 48 shows an image of two 300 μm thick EXG glasses drilled in this way.

Fig. 49 shows the same part after acid etching. In this case the diameter of the holes would appear to be 150 microns from a side profile, but in practice the diameter would be about 70 microns, just as it would appear larger from a side view, because there are rows of holes extending away from the camera focal plane, and each row is slightly offset laterally, which creates the illusion of larger holes than actually. The top view of the holes (fig. 50) shows that the holes are actually about 70 microns in diameter and that light passing through the center of each hole indicates that they are open through holes.

Example 5

150 micron thick corning with damage trace

The glass part was placed vertically in an acid etching bath containing 5% HF/7.5% HNO by volume₃. The part was etched at 26c for 810 seconds to remove about 13 microns of material at a rate of 1 micron/minute. Ultrasonic agitation at a combination of 40kHz and 80kHz frequencies was used to facilitate permeation and fluid exchange of fluids in the pores. In addition, the part is continuously moved in the x, y and z directions within the ultrasonic field to prevent standing wave patterns from the ultrasonic field from forming "hot spots" or cavitation related damage on the part and to provide macroscopic fluid flow across the part. During the etching process, the damage traces are enlarged to form the following through holes: the diameter was 13 microns, the aspect ratio was 11:1, and the waist diameter was 73% of the average of the diameters of the via openings at the top and bottom surfaces of the glass part. Fig. 57 is an optical photograph of a side view of a glass part after acid etching.

The relevant teachings of all patents, patent application publications, and references cited herein are incorporated by reference in their entirety.

Although exemplary embodiments have been described herein, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the scope encompassed by the appended claims.

Claims (18)

1. A glass article, comprising:

a substrate having a plurality of damage tracks, wherein the damage tracks have a diameter of less than 1 micron, a spacing between adjacent damage tracks is at least 20 microns, and an aspect ratio of 20:1 or greater.

2. An article of manufacture, comprising:

a substrate having a plurality of etched vias extending continuously from a first surface of the substrate to a second surface of the substrate, wherein:

the substrate is transparent to at least one wavelength from 390nm to 700 nm;

the plurality of etched vias are 20 microns or less in diameter;

the spacing between adjacent etched vias is 10 microns or greater;

the plurality of etched vias comprise openings in the first surface, openings in the second surface, and waists between the openings in the first surface and the openings in the second surface;

the waist diameter is at least 50% of the diameter of the opening in the first surface or the opening in the second surface; and

the difference between the diameter of the opening in the first surface and the diameter of the opening in the second surface is 3 microns or less.

3. The article of claim 2, wherein the plurality of etched vias have a diameter greater than 5 microns.

4. The article of claim 2, wherein the waist diameter is at least 70% of the diameter of the opening in the first surface or the opening in the second surface.

5. The article of claim 4, wherein the waist diameter is at least 75% of the diameter of the opening in the first surface or the opening in the second surface.

6. The article of claim 5, wherein the waist diameter is at least 80% of the diameter of the opening in the first surface or the opening in the second surface.

7. The article of claim 2, wherein the substrate is fused quartz.

8. The article according to claim 2, wherein the substrate is glass.

9. The article according to claim 8, wherein the glass is a chemically strengthened glass.

10. The article of claim 2, wherein the substrate has a thickness of 1mm or less.

11. The article of claim 2, wherein the substrate has a thickness of 20 microns to 200 microns.

12. The article of claim 2, wherein the density of the plurality of etched vias is 5 vias/mm²-50 through holes/mm²。

13. The article of claim 2, wherein the plurality of etched vias have a diameter of less than or equal to 15 microns.

14. The article of claim 2, wherein the plurality of etched vias have a diameter of less than or equal to 10 microns.

15. The article of claim 2, wherein the aspect ratio of the plurality of etched vias is 5:1 to 20: 1.

16. The article of claim 2, wherein the plurality of etched vias comprise a conductive material.

17. The article of claim 2, wherein the plurality of etched vias have a roundness of less than 5 μ ι η at least one of the first surface and the second surface.

18. The article of claim 2, wherein an aspect ratio of a substrate thickness to a diameter at the first surface of at least a portion of the plurality of etched vias is 1:1 or greater.

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